Sample records for important chemical reactions

  1. Spectroscopy and reactions of molecules important in chemical evolution

    NASA Technical Reports Server (NTRS)

    Becker, R. S.

    1974-01-01

    The research includes: (1) hot hydrogen atom reactions in terms of the nature of products produced, mechanism of the reactions and the implication and application of such reactions for molecules existing in interstellar clouds, in planetary atmospheres, and in chemical evolution; (2) photochemical reactions that can lead to molecules important in chemical evolution, interstellar clouds and as constituents in planetary atmospheres; and (3) spectroscopic and theoretical properties of biomolecules and their precursors and where possible, use these to understand their photochemical behavior.

  2. Chemical Reactions

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2009-05-01

    We don't often stop to think about it, but underlying many of our everyday activities are chemical reactions. From the cooking of an egg to the growth of a child, chemical reactions make things happen. Although many of the reactions that support our lives

  3. Chemical Reactions

    NSDL National Science Digital Library

    Mrs. Hicken

    2009-05-04

    We are going go over a general view of reactions to prepare us for our unit on Chemical Reactions! Have fun learning! WARNING: If you are caught looking at ANY other site, without permission, you will be sent to the ALC, and you will not participate in any other computer activities for the rest of the year. Get your worksheet and begin! Overview Take this quiz and have me come over and sign off on your worksheet when you have completed the quiz! Overview Quiz Next let's take a look at what effect the rate of a chemical reaction. Rates of Reactions Another quiz, another check off by me! Rates of Reactions Quiz Now how do we measure how fast a ...

  4. Importance of cytochromes in cyclization reactions: quantum chemical study on a model reaction of proguanil to cycloguanil.

    PubMed

    Arfeen, Minhajul; Patel, Dhilon S; Abbat, Sheenu; Taxak, Nikhil; Bharatam, Prasad V

    2014-10-30

    Proguanil, an anti-malarial prodrug, undergoes cytochrome P450 catalyzed biotransformation to the pharmacologically active triazine metabolite (cycloguanil), which inhibits plasmodial dihydrofolate reductase. This cyclization is catalyzed by CYP2C19 and many anti-malarial lead compounds are being designed and synthesized to exploit this pathway. Quantum chemical calculations were performed using the model species (Cpd I for active species of cytochrome and N4-isopropyl-N6-methylbiguanide for proguanil) to elucidate the mechanism of the cyclization pathway. The overall reaction involves the loss of a water molecule, and is exothermic by approximately 55 kcal/mol, and involves a barrier of approximately 17 kcal/mol. The plausible reaction pathway involves the initial H-radical abstraction from the isopropyl group by Cpd I, followed by two alternative paths- (i) oxygen rebound to provide hydroxyl derivative and (ii) loss of additional H-radical to yield 1,3,5-triazatriene, which undergoes cyclization. This study helped in understanding the role of the active species of cytochromes in this important cyclization reaction. PMID:25196060

  5. Studies of Elementary Reactions of Chemical Importance in the Atmospheres of Planets

    NASA Technical Reports Server (NTRS)

    Nesbitt, Fred L.

    2001-01-01

    The methyl self-reaction was studied at T = 298 K and 202 K and at three different pressures, P = 0.5, 1.0, and 2.1 Torr. The experimental measurements were performed in our discharge flow-mass spectrometer (DF-MS) apparatus. The methyl radicals were generated by the reaction of F with methane. Passing a mixture of molecular fluorine, F2, in helium through a microwave cavity generated the atomic fluorine reagent. The atomic F enters the flow tube through a rear port on the flow tube. The methane reagent enters the flow tube through a movable injector located coaxial in the flow tube. The decay of methyl radical signal was monitored at a mass/charge ratio (m/z) of 15 as a function of the injector distance. To minimize secondary chemistry from the reaction CH3 + F to CH2 + HF the initial [CH4](sub 0)/[F](sub 0) was above 37.0 and typically 100. This ensures a 1:1 relationship between initial [F] and [CH3]. A titration of F with excess Cl2 yields the initial [F](sub 0). Our experimental methodology to accurately measure the mass spectrometer scaling factor, i.e., the relationship between initial signal and [CH3](sub 0) has been improved. Now we measure the CH3 signal decay under exponential decay conditions at low initial [F](sub 0), 3x10(exp 11) molecule/cc, in the presence of Cl2. This minimizes the second-order decay contributed by the CH3 self-reaction and a simple extrapolation of the 1n(signal) vs time plot to t = 0 gives the initial signal. This provides the desired relationship between initial signal at 15 amu and [CH3](sub 0). The resulting calibration is then applied to the observed decay of the CH3 signal at high concentrations of CH3 assuming linearity of this scaling factor.

  6. Chemical Reactions at Surfaces

    SciTech Connect

    Michael Henderson and Nancy Ryan Gray

    2010-04-14

    Chemical reactions at surfaces underlie some of the most important processes of today, including catalysis, energy conversion, microelectronics, human health and the environment. Understanding surface chemical reactions at a fundamental level is at the core of the field of surface science. The Gordon Research Conference on Chemical Reactions at Surfaces is one of the premiere meetings in the field. The program this year will cover a broad range of topics, including heterogeneous catalysis and surface chemistry, surfaces in environmental chemistry and energy conversion, reactions at the liquid-solid and liquid-gas interface, electronic materials growth and surface modification, biological interfaces, and electrons and photons at surfaces. An exciting program is planned, with contributions from outstanding speakers and discussion leaders from the international scientific community. The conference provides a dynamic environment with ample time for discussion and interaction. Attendees are encouraged to present posters; the poster sessions are historically well attended and stimulate additional discussions. The conference provides an excellent opportunity for junior researchers (e.g. graduate students or postdocs) to present their work and interact with established leaders in the field.

  7. Chemical Reactions and Stoichiometry

    NSDL National Science Digital Library

    2012-07-31

    In this activity, students explore reactions in which chemical bonds are formed and broken. Students experiment with changing the temperature and the concentration of the atoms in order to see how these affect reaction rates. They also learn how to communicate what happens during a chemical reaction by writing the ratios of reactants and products, known as stoichiometry.

  8. Concordant Chemical Reaction Networks

    E-print Network

    Shinar, Guy

    2011-01-01

    We describe a large class of chemical reaction networks, those endowed with a subtle structural property called concordance. We show that the class of concordant networks coincides precisely with the class of networks which, when taken with any weakly monotonic kinetics, invariably give rise to kinetic systems that are injective --- a quality that, among other things, precludes the possibility of switch-like transitions between distinct positive steady states. We also provide persistence characteristics of concordant networks, instability implications of discordance, and consequences of stronger variants of concordance. Some of our results are in the spirit of recent ones by Banaji and Craciun, but here we do not require that every species suffer a degradation reaction. This is especially important in studying biochemical networks, for which it is rare to have all species degrade.

  9. General Biology 1, Reactions 1 CHEMICAL REACTIONS *

    E-print Network

    Prestwich, Ken

    General Biology 1, Reactions 1 CHEMICAL REACTIONS * Note: This is the first of a two-part set of notes. This set will review chemical reactions and the next will overview enzymes. What you learn and ribozymes. At their heart, organisms are complex chemical engines. However, many of the chemical reactions

  10. Intro Biology, Reactions 1 CHEMICAL REACTIONS *

    E-print Network

    Prestwich, Ken

    Intro Biology, Reactions 1 CHEMICAL REACTIONS * Note: This is the first of a two-part set of notes. This set will review chemical reactions and the next will overview enzymes. What you learn in these two and ribozymes. At their heart, organisms are complex chemical engines. However, many of the chemical reactions

  11. Chemical ReactionsChemical Reactions between the Componentsbetween the Components

    E-print Network

    Beauchamp, Jack

    1 Chemical ReactionsChemical Reactions between the Componentsbetween the Components of MolecularMethodology We induce chemical reactions in molecular aggregates by collisionally activating the clusters of AMP to ATP by CID: Julian, RJ and J.L. Beauchamp IJMS 2003, 227(1), 147-159. Reaction of Gas

  12. Categorizing Chemical Reactions

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2009-07-10

    Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the second of four Science Objects in the Chemical Reactions SciPack. It provides an

  13. Rates of Chemical Reactions

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    1900-01-01

    Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the third of four Science Objects in the Chemical Reactions SciPack. It demonstrates

  14. Ultrafast Laser Spectroscopyof Chemical Reactions

    E-print Network

    Zewail, Ahmed

    Ultrafast Laser Spectroscopyof Chemical Reactions - Joseph L. Kneeand AhmedH. Zewail California of chemical physics is to understand how chemi- cal reactions complete their journey from reactants to prod at the molecular level. The making of new bonds (and the breaking of old ones) in elementary chemical reactions

  15. Chemical Reactions in DSMC

    NASA Astrophysics Data System (ADS)

    Bird, G. A.

    2011-05-01

    DSMC simulations of chemically reacting gas flows have generally employed procedures that convert the macroscopic chemical rate equations to reaction cross-sections at the microscopic level. They therefore depend on the availability of experimental data that has been fitted to equations of the Arrhenius form. This paper presents a physical model for dissociation and recombination reactions and a phenomenological model for exchange and chain reactions. These are based on the vibrational states of the colliding molecules and do not require any experimentally-based data. The simplicity of the models allows the corresponding rate equations to be written down and, while these are not required for the implementation of the models, they facilitate their validation. The model is applied to a typical hypersonic atmospheric entry problem and the results are compared with the corresponding results from the traditional method. It is also used to investigate both spontaneous and forced ignition as well as the structure of a deflagration wave in an oxygen-hydrogen mixture.

  16. Magnetic Effects in Chemical Reactions

    Microsoft Academic Search

    Anatolii L Buchachenko

    1976-01-01

    The Review discusses in what elementary chemical reactions the intrinsic angular momentum of electrons and nuclei is conserved and in what reactions it is not conserved, how weak electron-nuclear magnetic interaction and an external magnetic field influence the conservation of angular momentum and what are the consequences of this effect, and what magnetic effects occur in chemical reactions, as well

  17. International chemical identifier for chemical reactions

    E-print Network

    Grethe, Guenter; Goodman, Jonathan; Allen, Chad

    2013-03-22

    ORAL PRESENTATION Open Access International chemical identifier for chemical reactions Guenter Grethe1*, Jonathan Goodman2, Chad Allen2 From 8th German Conference on Chemoinformatics: 26 CIC-Workshop Goslar, Germany. 11-13 November 2012 An open... -access software for creating a unique, text-based identifier for reactions (RInChI) was developed by the Goodman group at the University of Cambridge, based on the IUPAC International Chemical Identifier (InChI) stan- dard. RInChIs describe the substances...

  18. Speeding chemical reactions by focusing

    E-print Network

    A. M. Lacasta; L. Ramirez-Piscina; J. M. Sancho; K. Lindenberg

    2012-12-13

    We present numerical results for a chemical reaction of colloidal particles which are transported by a laminar fluid and are focused by periodic obstacles in such a way that the two components are well mixed and consequently the chemical reaction is speeded up. The roles of the various system parameters (diffusion coefficients, reaction rate, obstacles sizes) are studied. We show that focusing speeds up the reaction from the diffusion limited rate (t to the power -1/2) to very close to the perfect mixing rate, (t to the power -1).

  19. Speeding chemical reactions by focusing

    E-print Network

    Lacasta, A M; Sancho, J M; Lindenberg, K

    2012-01-01

    We present numerical results for a chemical reaction of colloidal particles which are transported by a laminar fluid and are focused by periodic obstacles in such a way that the two components are well mixed and consequently the chemical reaction is speeded up. The roles of the various system parameters (diffusion coefficients, reaction rate, obstacles sizes) are studied. We show that focusing speeds up the reaction from the diffusion limited rate (t to the power -1/2) to very close to the perfect mixing rate, (t to the power -1).

  20. Geometric description of chemical reactions

    E-print Network

    Hernando Quevedo; Diego Tapias

    2013-01-02

    We use the formalism of Geometrothermodynamics to describe chemical reactions in the context of equilibrium thermodynamics. Any chemical reaction in a closed system is shown to be described by a geodesic in a $2-$dimensional manifold that can be interpreted as the equilibrium space of the reaction. We first show this in the particular cases of a reaction with only two species corresponding to either two ideal gases or two van der Waals gases. We then consider the case of a reaction with an arbitrary number of species. The initial equilibrium state of the geodesic is determined by the initial conditions of the reaction. The final equilibrium state, which follows from a thermodynamic analysis of the reaction, is shown to correspond to a coordinate singularity of the thermodynamic metric which describes the equilibrium manifold.

  1. Geometric description of chemical reactions

    E-print Network

    Quevedo, Hernando

    2013-01-01

    We use the formalism of Geometrothermodynamics to describe chemical reactions in the context of equilibrium thermodynamics. Any chemical reaction in a closed system is shown to be described by a geodesic in a $2-$dimensional manifold that can be interpreted as the equilibrium space of the reaction. We first show this in the particular cases of a reaction with only two species corresponding to either two ideal gases or two van der Waals gases. We then consider the case of a reaction with an arbitrary number of species. The initial equilibrium state of the geodesic is determined by the initial conditions of the reaction. The final equilibrium state, which follows from a thermodynamic analysis of the reaction, is shown to correspond to a coordinate singularity of the thermodynamic metric which describes the equilibrium manifold.

  2. Chemical burn or reaction

    MedlinePLUS

    ... the skin has come in contact with the toxic substance Rash , blisters , burns on the skin Unconsciousness ... locked cabinet. Avoid mixing different products that contain toxic chemicals such as ammonia and bleach. The mixture ...

  3. Exact Stochastic Simulation of Coupled Chemical Reactions Daniel T. Gillesple

    E-print Network

    Saidak, Filip

    2340 Exact Stochastic Simulation of Coupled Chemical Reactions Daniel T. Gillesple Danlel T chemical reaction channels, then given the numbers of molecules of each species present at some initial importance and usefulness of the differential reaction-rate equations approach to chemical kinetics cannot

  4. LEGO® Chemical Reactions

    NSDL National Science Digital Library

    Kathleen M. Vandiver, Ph.D.

    2009-01-01

    This activity uses LEGO® bricks to represent atoms bonding into molecules and crystals. The lesson plan is for a 2.5 hour workshop (or four 45-minute classes). There is a "wet lab" chemistry experiment (mixing baking soda and calcium chloride with phenol red indicator), followed by a "LEGO lab" modeling phase that includes writing formulas using chemical notation. This lesson is also offered as a 2.5 hour field trip lesson at the MIT Edgerton Center.

  5. Computed potential energy surfaces for chemical reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1994-01-01

    Quantum mechanical methods have been used to compute potential energy surfaces for chemical reactions. The reactions studied were among those believed to be important to the NASP and HSR programs and included the recombination of two H atoms with several different third bodies; the reactions in the thermal Zeldovich mechanism; the reactions of H atom with O2, N2, and NO; reactions involved in the thermal De-NO(x) process; and the reaction of CH(squared Pi) with N2 (leading to 'prompt NO'). These potential energy surfaces have been used to compute reaction rate constants and rates of unimolecular decomposition. An additional application was the calculation of transport properties of gases using a semiclassical approximation (and in the case of interactions involving hydrogen inclusion of quantum mechanical effects).

  6. Experimental Demonstrations in Teaching Chemical Reactions.

    ERIC Educational Resources Information Center

    Hugerat, Muhamad; Basheer, Sobhi

    2001-01-01

    Presents demonstrations of chemical reactions by employing different features of various compounds that can be altered after a chemical change occurs. Experimental activities include para- and dia-magnetism in chemical reactions, aluminum reaction with base, reaction of acid with carbonates, use of electrochemical cells for demonstrating chemical

  7. Homeostasis in Chemical Reaction Pathways

    E-print Network

    Malyshev, V A; Zamyatin, A A

    2011-01-01

    We consider stochastic models of chemical reaction networks with time dependent input rates and several types of molecules. We prove that, in despite of strong time dependence of input rates, there is a kind of homeostasis phenomenon: far away from input nodes the mean numbers of molecules of each type become approximately constant (do not depend on time).

  8. Homeostasis in Chemical Reaction Pathways

    E-print Network

    V. A. Malyshev; A. D. Manita; A. A. Zamyatin

    2011-12-25

    We consider stochastic models of chemical reaction networks with time dependent input rates and several types of molecules. We prove that, in despite of strong time dependence of input rates, there is a kind of homeostasis phenomenon: far away from input nodes the mean numbers of molecules of each type become approximately constant (do not depend on time).

  9. Nanomotors Propelled by Chemical Reactions

    NASA Astrophysics Data System (ADS)

    Kapral, Raymond

    2013-12-01

    Molecular motors, like their macroscopic counterparts, consume energy and convert it to work; however, unlike macroscopic motors, they are subject to strong fluctuations and do not rely on inertia for their operation. In this chapter, the dynamics of synthetic chemically-powered nanomotors and mechanisms by which they operate are described. The focus is on motors that propel themselves by utilizing fuel in the environment to generate their own concentration gradients through chemical reactions. Macroscopic diffusiophoretic mechanisms for such motions are discussed, as well as microscopic and mesoscopic descriptions of motor dynamics.

  10. Visualization of chemical reaction dynamics: Toward understanding complex polyatomic reactions

    PubMed Central

    SUZUKI, Toshinori

    2013-01-01

    Polyatomic molecules have several electronic states that have similar energies. Consequently, their chemical dynamics often involve nonadiabatic transitions between multiple potential energy surfaces. Elucidating the complex reactions of polyatomic molecules is one of the most important tasks of theoretical and experimental studies of chemical dynamics. This paper describes our recent experimental studies of the multidimensional multisurface dynamics of polyatomic molecules based on two-dimensional ion/electron imaging. It also discusses ultrafast photoelectron spectroscopy of liquids for elucidating nonadiabatic electronic dynamics in aqueous solutions. PMID:23318678

  11. THEORY OF CHEMICAL REACTION ANTONIO LAGANA

    E-print Network

    Auzinsh, Marcis

    THEORY OF CHEMICAL REACTION DYNAMICS Edited by: ANTONIO LAGANA Department of Chemistry University Theoretical treatment of the dynamics of chemical reactions has undergone a spectacular development during the NATO Advanced Research Work- shop on the Theory of the Dynamics of Chemical Reactions in Balatonf

  12. GENERALIZED TOPOLOGIES: HYPERGRAPHS, CHEMICAL REACTIONS, AND

    E-print Network

    Flamm, Christoph

    GENERALIZED TOPOLOGIES: HYPERGRAPHS, CHEMICAL REACTIONS, AND BIOLOGICAL EVOLUTION Christoph Flamm1;INTRODUCTION Investigations into general principles underlying chemical reaction networks, molecular [21, 66, 62, 31, 59, 56, 22, 60]. Chemical Reaction Networks. We start from a fixed set X of molecular

  13. Leaderless deterministic chemical reaction networks Monir Hajiaghayi

    E-print Network

    Doty, David

    Leaderless deterministic chemical reaction networks David Doty Monir Hajiaghayi Abstract This paper is deterministically computable by a stochastic chemical reaction network (CRN) if and only if the graph of f in a well-mixed solution, the language of chemical reaction networks (CRNs) is an attractive choice. A CRN

  14. Collisions, Chemical Reactions, and Transport Chemistry 223

    E-print Network

    Ronis, David M.

    Collisions, Chemical Reactions, and Transport Chemistry 223 David Ronis McGill University 1 for a number of practical con- siderations; e.g., if a chemical reaction takes place every time a molecule hits, introduced earlier. Aside from the previously mentioned example of chemical reaction on a surface, another

  15. Physics 112 Equilibrium in Chemical Reactions

    E-print Network

    Young, A. Peter

    Physics 112 Equilibrium in Chemical Reactions Peter Young I. FORMALISM This is a considerably that it is indeed a minimum. In this handout we discuss chemical reactions, which take place not at constant volume next give some examples of chemical reactions which we will use to illustrate the theory in what

  16. Theory of chemical reaction dynamics. Volume 4

    SciTech Connect

    Baer, M.

    1985-01-01

    This book examines some of the basic principles behind chemical reaction kinetics. Topics considered include generalized transition state theory, statistical dynamics, the theory of reactions at a solid surface, and the theory of reactions in solution.

  17. Minimum Energy Pathways for Chemical Reactions

    NASA Technical Reports Server (NTRS)

    Walch, S. P.; Langhoff, S. R. (Technical Monitor)

    1995-01-01

    Computed potential energy surfaces are often required for computation of such parameters as rate constants as a function of temperature, product branching ratios, and other detailed properties. We have found that computation of the stationary points/reaction pathways using CASSCF/derivative methods, followed by use of the internally contracted CI method to obtain accurate energetics, gives useful results for a number of chemically important systems. The talk will focus on a number of applications to reactions leading to NOx and soot formation in hydrocarbon combustion.

  18. M. Bahrami ENSC 461 (S 11) Chemical Reactions 1 Chemical Reactions

    E-print Network

    Bahrami, Majid

    M. Bahrami ENSC 461 (S 11) Chemical Reactions 1 Chemical Reactions When analyzing reacting systemsHm. For example octane is C8H18. Combustion: is a chemical reaction during which a fuel is oxidized and a large.28 #12;M. Bahrami ENSC 461 (S 11) Chemical Reactions 2 Where N is the number of moles and M is the molar

  19. A Method for IncorporatingA Method for Incorporating Chemical Reactions intoChemical Reactions into

    E-print Network

    Politècnica de Catalunya, Universitat

    A Method for IncorporatingA Method for Incorporating Chemical Reactions intoChemical Reactions Vilarrasa, Francesca De Gaspari, Orlando Silva, Jesús Carrera #12;Introduction "Chemical reactions" in CODE), CO3 2-, OH- 5 Chemical reactions: CaCO3(s) + H+ = Ca2+ + HCO3 - CO2(aq) = CO2(g) H+ + HCO3 - = H2

  20. Timing in chemical reaction networks Chemical reaction networks (CRNs) formally model chem-

    E-print Network

    Doty, David

    Timing in chemical reaction networks David Doty Abstract Chemical reaction networks (CRNs) formally the interactions of molecular species in a well-mixed solution is that of (fi- nite) chemical reaction networks (CRNs), i.e., finite sets of chemical reactions such as A+B A+C. When the behavior of individual

  1. A reversible nanoconfined chemical reaction.

    PubMed

    Nielsen, Thomas K; Bösenberg, Ulrike; Gosalawit, Rapee; Dornheim, Martin; Cerenius, Yngve; Besenbacher, Flemming; Jensen, Torben R

    2010-07-27

    Hydrogen is recognized as a potential, extremely interesting energy carrier system, which can facilitate efficient utilization of unevenly distributed renewable energy. A major challenge in a future "hydrogen economy" is the development of a safe, compact, robust, and efficient means of hydrogen storage, in particular, for mobile applications. Here we report on a new concept for hydrogen storage using nanoconfined reversible chemical reactions. LiBH4 and MgH2 nanoparticles are embedded in a nanoporous carbon aerogel scaffold with pore size Dmax approximately 21 nm and react during release of hydrogen and form MgB2. The hydrogen desorption kinetics is significantly improved compared to bulk conditions, and the nanoconfined system has a high degree of reversibility and stability and possibly also improved thermodynamic properties. This new scheme of nanoconfined chemistry may have a wide range of interesting applications in the future, for example, within the merging area of chemical storage of renewable energy. PMID:20533850

  2. Plasmon-driven sequential chemical reactions in an aqueous environment

    PubMed Central

    Zhang, Xin; Wang, Peijie; Zhang, Zhenglong; Fang, Yurui; Sun, Mengtao

    2014-01-01

    Plasmon-driven sequential chemical reactions were successfully realized in an aqueous environment. In an electrochemical environment, sequential chemical reactions were driven by an applied potential and laser irradiation. Furthermore, the rate of the chemical reaction was controlled via pH, which provides indirect evidence that the hot electrons generated from plasmon decay play an important role in plasmon-driven chemical reactions. In acidic conditions, the hot electrons were captured by the abundant H+ in the aqueous environment, which prevented the chemical reaction. The developed plasmon-driven chemical reactions in an aqueous environment will significantly expand the applications of plasmon chemistry and may provide a promising avenue for green chemistry using plasmon catalysis in aqueous environments under irradiation by sunlight. PMID:24958029

  3. Plasmon-driven sequential chemical reactions in an aqueous environment.

    PubMed

    Zhang, Xin; Wang, Peijie; Zhang, Zhenglong; Fang, Yurui; Sun, Mengtao

    2014-01-01

    Plasmon-driven sequential chemical reactions were successfully realized in an aqueous environment. In an electrochemical environment, sequential chemical reactions were driven by an applied potential and laser irradiation. Furthermore, the rate of the chemical reaction was controlled via pH, which provides indirect evidence that the hot electrons generated from plasmon decay play an important role in plasmon-driven chemical reactions. In acidic conditions, the hot electrons were captured by the abundant H(+) in the aqueous environment, which prevented the chemical reaction. The developed plasmon-driven chemical reactions in an aqueous environment will significantly expand the applications of plasmon chemistry and may provide a promising avenue for green chemistry using plasmon catalysis in aqueous environments under irradiation by sunlight. PMID:24958029

  4. Learning to Predict Chemical Reactions

    PubMed Central

    Kayala, Matthew A.; Azencott, Chloé-Agathe; Chen, Jonathan H.

    2011-01-01

    Being able to predict the course of arbitrary chemical reactions is essential to the theory and applications of organic chemistry. Approaches to the reaction prediction problems can be organized around three poles corresponding to: (1) physical laws; (2) rule-based expert systems; and (3) inductive machine learning. Previous approaches at these poles respectively are not high-throughput, are not generalizable or scalable, or lack sufficient data and structure to be implemented. We propose a new approach to reaction prediction utilizing elements from each pole. Using a physically inspired conceptualization, we describe single mechanistic reactions as interactions between coarse approximations of molecular orbitals (MOs) and use topological and physicochemical attributes as descriptors. Using an existing rule-based system (Reaction Explorer), we derive a restricted chemistry dataset consisting of 1630 full multi-step reactions with 2358 distinct starting materials and intermediates, associated with 2989 productive mechanistic steps and 6.14 million unproductive mechanistic steps. And from machine learning, we pose identifying productive mechanistic steps as a statistical ranking, information retrieval, problem: given a set of reactants and a description of conditions, learn a ranking model over potential filled-to-unfilled MO interactions such that the top ranked mechanistic steps yield the major products. The machine learning implementation follows a two-stage approach, in which we first train atom level reactivity filters to prune 94.00% of non-productive reactions with a 0.01% error rate. Then, we train an ensemble of ranking models on pairs of interacting MOs to learn a relative productivity function over mechanistic steps in a given system. Without the use of explicit transformation patterns, the ensemble perfectly ranks the productive mechanism at the top 89.05% of the time, rising to 99.86% of the time when the top four are considered. Furthermore, the system is generalizable, making reasonable predictions over reactants and conditions which the rule-based expert does not handle. A web interface to the machine learning based mechanistic reaction predictor is accessible through our chemoinformatics portal (http://cdb.ics.uci.edu) under the Toolkits section. PMID:21819139

  5. Classes of Chemical Reactions Reactions in aqueous media

    E-print Network

    Zakarian, Armen

    Classes of Chemical Reactions Reactions in aqueous media · Precipitation reactions · Acid + electrolytes: a substance that conducts an electric current when dissolved in water Acids are donors of H+ (this is a definition) HBr ! H3O+ + Br¯ or HBr ! H+ + Br¯ Equations for Aqueous Ionic Reactions

  6. Chemical reactions at aqueous interfaces

    NASA Astrophysics Data System (ADS)

    Vecitis, Chad David

    2009-12-01

    Interfaces or phase boundaries are a unique chemical environment relative to individual gas, liquid, or solid phases. Interfacial reaction mechanisms and kinetics are often at variance with homogeneous chemistry due to mass transfer, molecular orientation, and catalytic effects. Aqueous interfaces are a common subject of environmental science and engineering research, and three environmentally relevant aqueous interfaces are investigated in this thesis: 1) fluorochemical sonochemistry (bubble-water), 2) aqueous aerosol ozonation (gas-water droplet), and 3) electrolytic hydrogen production and simultaneous organic oxidation (water-metal/semiconductor). Direct interfacial analysis under environmentally relevant conditions is difficult, since most surface-specific techniques require relatively `extreme' conditions. Thus, the experimental investigations here focus on the development of chemical reactors and analytical techniques for the completion of time/concentration-dependent measurements of reactants and their products. Kinetic modeling, estimations, and/or correlations were used to extract information on interfacially relevant processes. We found that interfacial chemistry was determined to be the rate-limiting step to a subsequent series of relatively fast homogeneous reactions, for example: 1) Pyrolytic cleavage of the ionic headgroup of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) adsorbed to cavitating bubble-water interfaces during sonolysis was the rate-determining step in transformation to their inorganic constituents carbon monoxide, carbon dioxide, and fluoride; 2) ozone oxidation of aqueous iodide to hypoiodous acid at the aerosol-gas interface is the rate-determining step in the oxidation of bromide and chloride to dihalogens; 3) Electrolytic oxidation of anodic titanol surface groups is rate-limiting for the overall oxidation of organics by the dichloride radical. We also found chemistry unique to the interface, for example: 1) Adsorption of dilute PFOS(aq) and PFOA(aq) to acoustically cavitating bubble interfaces was greater than equilibrium expectations due to high-velocity bubble radial oscillations; 2) Relative ozone oxidation kinetics of aqueous iodide, sulfite, and thiosulfate were at variance with previously reported bulk aqueous kinetics; 3) Organics that directly chelated with the anode surface were oxidized by direct electron transfer, resulting in immediate carbon dioxide production but slower overall oxidation kinetics. Chemical reactions at aqueous interfaces can be the rate-limiting step of a reaction network and often display novel mechanisms and kinetics as compared to homogeneous chemistry.

  7. Chemical Reactions Directed Peptide Self-Assembly

    PubMed Central

    Rasale, Dnyaneshwar B.; Das, Apurba K.

    2015-01-01

    Fabrication of self-assembled nanostructures is one of the important aspects in nanoscience and nanotechnology. The study of self-assembled soft materials remains an area of interest due to their potential applications in biomedicine. The versatile properties of soft materials can be tuned using a bottom up approach of small molecules. Peptide based self-assembly has significant impact in biology because of its unique features such as biocompatibility, straight peptide chain and the presence of different side chain functionality. These unique features explore peptides in various self-assembly process. In this review, we briefly introduce chemical reaction-mediated peptide self-assembly. Herein, we have emphasised enzymes, native chemical ligation and photochemical reactions in the exploration of peptide self-assembly. PMID:25984603

  8. Chemical reactions directed Peptide self-assembly.

    PubMed

    Rasale, Dnyaneshwar B; Das, Apurba K

    2015-01-01

    Fabrication of self-assembled nanostructures is one of the important aspects in nanoscience and nanotechnology. The study of self-assembled soft materials remains an area of interest due to their potential applications in biomedicine. The versatile properties of soft materials can be tuned using a bottom up approach of small molecules. Peptide based self-assembly has significant impact in biology because of its unique features such as biocompatibility, straight peptide chain and the presence of different side chain functionality. These unique features explore peptides in various self-assembly process. In this review, we briefly introduce chemical reaction-mediated peptide self-assembly. Herein, we have emphasised enzymes, native chemical ligation and photochemical reactions in the exploration of peptide self-assembly. PMID:25984603

  9. Invited Review Biologically Relevant Chemical Reactions of

    E-print Network

    Gates, Kent. S.

    Invited Review Biologically Relevant Chemical Reactions of N7-Alkylguanine Residues in DNA Kent S set out here to provide an overview of the biologically relevant chemical reactions of N7-alkylgua-Catalyzed Depurination 841 3.2. Chemical Mechanism for the Depurination of N7-Alkylguanine Residues 842 3.3. Overview

  10. Quantum Theory of Fast Chemical Reactions

    SciTech Connect

    Light, John C

    2007-07-30

    The aims of the research under this grant were to develop a theoretical understanding and predictive abiility for a variety of processes occurring in the gas phase. These included bimolecular chemical exchange reactions, photodissociation, predissociation resonances, unimolecular reactions and recombination reactions. In general we assumed a knowledge, from quantum chemistry, of the interactions of the atoms and molecular fragments involved. Our focus was primarily on the accurate (quantum) dynamics of small molecular systems. This has been important for many reactions related to combustion and atmospheric chemistry involving light atom transfer reactions and, for example, resonances in dissociation and recombination reactions. The rates of such reactions, as functions of temperature, internal states, and radiation (light), are fundamental for generating models of overall combustion processes. A number of new approaches to these problems were developed inclluding the use of discrete variable representations (DVR's) for evaluating rate constants with the flux-flux correlation approach, finite range approaches to exact quantum scattering calculations, energy selected basis representations, transition state wave packet approaches and improved semiclassical approaches. These (and others) were applied to a number of reactive systems and molecular systems of interest including (many years ago) the isotopic H + H2 exchange reactions, the H2 + OH (and H + H2O) systems, Ozone resonances, van der Waals molecule reactions, etc. A total of 7 graduate students, and 5 post-doctoral Research Associates were supported, at least in part, under this grant and seven papers were published with a total of 10 external collaborators. The majority of the 36 publications under this grant were supported entirely by DOE.

  11. Reaction efficiency effects on binary chemical reactions.

    PubMed

    Lazaridis, Filippos; Savara, Aditya; Argyrakis, Panos

    2014-09-14

    We study the effect of the variation of reaction efficiency in binary reactions. We use the well-known A + B ? 0 model, which has been extensively studied in the past. We perform simulations on this model where we vary the efficiency of reaction, i.e., when two particles meet they do not instantly react, as has been assumed in previous studies, but they react with a probability ?, where ? is in the range 0 < ? < 1. Our results show that at small ? values the system is reaction limited, but as ? increases it crosses over to a diffusion limited behavior. At early times, for small ? values, the particle density falls slower than for larger ? values. This fall-off goes over a crossover point, around the value of ? = 0.50 for high initial densities. Under a variety of conditions simulated, we find that the crossover point was dependent on the initial concentration but not on the lattice size. For intermediate and long times simulations, all ? values (in the depleted reciprocal density versus time plot) converge to the same behavior. These theoretical results are useful in models of epidemic reactions and epidemic spreading, where a contagion from one neighbor to the next is not always successful but proceeds with a certain probability, an analogous effect with the reaction probability examined in the current work. PMID:25217900

  12. Nuclear physics reactions of astrophysical importance

    NASA Astrophysics Data System (ADS)

    O'Malley, Patrick D.

    Understanding the origin of elements in the universe is one of the main goals of nuclear science and astrophysics today. Achieving this goal involves determining how the elements and their isotopes formed and being able to predict their abundances. At the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL), an experimental program has been established to use transfer reactions (such as (p,d) or (d,p)) to study the properties of many nuclei important to understanding the origins of various elements. Three measurements were done to aid in the determination of the origins of different light isotopes. Big Bang Nucleosynthesis calculations, constrained by the Wilkinson Microwave Anisotropy Probe results, produce primordial 7Li abundances almost a factor of four larger than those extrapolated from observations. Since primordial 7Li is believed to be mostly produced by the beta decay of 7Be, one proposed solution to this discrepancy is a resonant enhancement of the 7Be(d, p)2? reaction rate through the 5/2+ 16.7-MeV state in 9B. The 2H(7Be,d) 7Be reaction was used to search for such a resonance; none was observed. An upper limit on the width of the proposed resonance was deduced. 19F is believed to have formed in Asymptotic Giant Branch stars, but current models cannot reproduce the observed abundances of this nucleus. One of the key reactions responsible for the creation of 19F is 15N(?,?). Therefore, it is important to understand reactions that might destroy 15N, such as 15N(n,?). The magnitude of the 15N( n,?) reaction rate depends directly on the neutron spectroscopic factors of low-lying 16N levels. Currently the measured spectroscopic factors differ from those expected from theory by a factor of 2. A study has been done to resolve this discrepancy using the d( 15N,p) reaction. The spectroscopic factors were all found to be close to unity which is in agreement with theoretical predictions. In novae, gamma ray emission is believed to be primarily due to electron-positron annihilation, though the source of these positrons remains a mystery. The positrons are believed to originate from the beta decay of 18F due to its long half-life (t1/2 ˜ 110 min.). To date, gamma rays from this nucleus have not been observed. Therefore, studies have been made on reactions believed to destroy 18F, such as 18F(p,?) which goes through states in 19Ne. A recent study by Adekola et al. showed that a state at 6.289-MeV in 19Ne, just below the proton threshold, could have a significant impact on this reaction rate. However, the spin of this state could not be determined. To determine the spin of this sub-threshold state, a study of the 20Ne(p,d ) reaction was made using a proton beam on a carbon foil implanted with 20Ne. Due target contaminants, a spin assignment could not be made, but a new experimental design was created and is described in this dissertation.

  13. 2005 Chemical Reactions at Surfaces

    SciTech Connect

    Cynthia M. Friend

    2006-03-14

    The Gordon Research Conference (GRC) on 2005 Chemical Reactions at Surfaces was held at Ventura Beach Marriott, Ventura California from February 13, 2005 through February 18, 2005. The Conference was well-attended with 124 participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students. In designing the formal speakers program, emphasis was placed on current unpublished research and discussion of the future target areas in this field. There was a conscious effort to stimulate lively discussion about the key issues in the field today. Time for formal presentations was limited in the interest of group discussions. In order that more scientists could communicate their most recent results, poster presentation time was scheduled. Attached is a copy of the formal schedule and speaker program and the poster program. In addition to these formal interactions, 'free time' was scheduled to allow informal discussions. Such discussions are fostering new collaborations and joint efforts in the field.

  14. Chemical reactions in low-g

    NASA Technical Reports Server (NTRS)

    Grodzka, P. G.; Facemire, B. R.

    1978-01-01

    The Apollo-Soyuz flight experiment, 'Chemical Foams' demonstrated that foams and air/liquid dispersions are much more stable in low-gravity than on the ground. It thus should be possible to conduct unique chemical reactions in space foams. The low-g results and subsequent ground work on the formaldehyde clock reaction indicate that the reaction is strongly influenced by (1) dissociated and undissociated solution species being adsorbed at solid/liquid and gas/liquid surfaces and (2) chemical reaction rates apparently being affected by long-range forces determined by the liquid mass and the extent and nature of all surface interfaces.

  15. Reaction Kinetics at High Pressure and Temperature: Effects on Milk Flavor Volatiles and on Chemical Compounds with Nutritional and Safety Importance in Several Foods

    Microsoft Academic Search

    Aurora Valdez-Fragoso; Hugo Mújica-Paz; Jorge Welti-Chanes; J. Antonio Torres

    2011-01-01

    Consumers demand, in addition to excellent eating quality, high standards of safety and nutrition in ready-to-eat food. This\\u000a requires a continuous improvement in conventional processing technologies and the development of new alternatives. Prevailing\\u000a technologies such as thermal processing can cause extensive and undesirable chemical changes in food composition while minimal\\u000a processing strategies cannot eliminate all microbial pathogens. This review focuses

  16. 'GREENER' CHEMICAL SYNTHESES USING ALTERNATE REACTION CONDITIONS

    EPA Science Inventory

    Microwave (MW) irradiation in conjunction with water as reaction media has proven to be a greener chemical approach for expeditious N-alkylation reactions of amines and hydrazines wherein the reactions under mildly basic conditions afford tertiary amines and double N-alkylation t...

  17. A Unified Theory of Chemical Reactions

    E-print Network

    Aubry, S

    2014-01-01

    We propose a new and general formalism for elementary chemical reactions where quantum electronic variables are used as reaction coordinates. This formalism is in principle applicable to all kinds of chemical reactions ionic or covalent. Our theory reveals the existence of an intermediate situation between ionic and covalent which may be almost barrierless and isoenegetic and which should be of high interest for understanding biochemistry.

  18. Mass Spectroscopy of Chemical Reaction of 3d Metal Clusters Involved in Chemical Vapor Deposition Synthesis of Carbon Nanotubes

    E-print Network

    Maruyama, Shigeo

    Mass Spectroscopy of Chemical Reaction of 3d Metal Clusters Involved in Chemical Vapor Deposition, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan The chemical reactions of transition metal importance. For example, these reactions are involved in the synthesis of single-walled carbon nanotubes

  19. Chemical reactions of organic compounds on clay surfaces.

    PubMed Central

    Soma, Y; Soma, M

    1989-01-01

    Chemical reactions of organic compounds including pesticides at the interlayer and exterior surfaces of clay minerals and with soil organic matter are reviewed. Representative reactions under moderate conditions possibly occurring in natural soils are described. Attempts have been made to clarify the importance of the chemical nature of molecules, their structures and their functional groups, and the Brönsted or Lewis acidity of clay minerals. PMID:2533556

  20. Chemical reaction equilibrium in nanoporous materials: NO dimerization reaction in carbon slit nanopores

    E-print Network

    Lisal, Martin

    Chemical reaction equilibrium in nanoporous materials: NO dimerization reaction in carbon slit of confinement on chemical reaction equilibrium in nanoporous materials. We use the reaction ensemble Monte Carlo of confinement on chemical properties, particularly on chemical reaction equilibria. A chemical reaction

  1. Conservation-dissipation structure of chemical reaction systems.

    PubMed

    Yong, Wen-An

    2012-12-01

    In this Brief Report, we show that balanced chemical reaction systems governed by the law of mass action have an elegant conservation-dissipation structure. From this structure a number of important conclusions can be easily deduced. In particular, with the help of this structure we can rigorously justify the classical partial equilibrium approximation in chemical kinetics. PMID:23368081

  2. Controlling chemical reactions of a single particle

    E-print Network

    Ratschbacher, Lothar; Sias, Carlo; Köhl, Michael

    2012-01-01

    The control of chemical reactions is a recurring theme in physics and chemistry. Traditionally, chemical reactions have been investigated by tuning thermodynamic parameters, such as temperature or pressure. More recently, physical methods such as laser or magnetic field control have emerged to provide completely new experimental possibilities, in particular in the realm of cold collisions. The control of reaction pathways is also a critical component to implement molecular quantum information processing. For these undertakings, single particles provide a clean and well-controlled experimental system. Here, we report on the experimental tuning of the exchange reaction rates of a single trapped ion with ultracold neutral atoms by exerting control over both their quantum states. We observe the influence of the hyperfine interaction on chemical reaction rates and branching ratios, and monitor the kinematics of the reaction products. These investigations advance chemistry with single trapped particles towards achi...

  3. Regimes of chemical reaction waves initiated by nonuniform initial conditions for detailed chemical reaction models.

    PubMed

    Liberman, M A; Kiverin, A D; Ivanov, M F

    2012-05-01

    Regimes of chemical reaction wave propagation initiated by initial temperature nonuniformity in gaseous mixtures, whose chemistry is governed by chain-branching kinetics, are studied using a multispecies transport model and a detailed chemical model. Possible regimes of reaction wave propagation are identified for stoichiometric hydrogen-oxygen and hydrogen-air mixtures in a wide range of initial pressures and temperature levels, depending on the initial non-uniformity steepness. The limits of the regimes of reaction wave propagation depend upon the values of the spontaneous wave speed and the characteristic velocities of the problem. It is shown that one-step kinetics cannot reproduce either quantitative neither qualitative features of the ignition process in real gaseous mixtures because the difference between the induction time and the time when the exothermic reaction begins significantly affects the ignition, evolution, and coupling of the spontaneous reaction wave and the pressure wave, especially at lower temperatures. We show that all the regimes initiated by the temperature gradient occur for much shallower temperature gradients than predicted by a one-step model. The difference is very large for lower initial pressures and for slowly reacting mixtures. In this way the paper provides an answer to questions, important in practice, about the ignition energy, its distribution, and the scale of the initial nonuniformity required for ignition in one or another regime of combustion wave propagation. PMID:23004867

  4. Regimes of chemical reaction waves initiated by nonuniform initial conditions for detailed chemical reaction models

    NASA Astrophysics Data System (ADS)

    Liberman, M. A.; Kiverin, A. D.; Ivanov, M. F.

    2012-05-01

    Regimes of chemical reaction wave propagation initiated by initial temperature nonuniformity in gaseous mixtures, whose chemistry is governed by chain-branching kinetics, are studied using a multispecies transport model and a detailed chemical model. Possible regimes of reaction wave propagation are identified for stoichiometric hydrogen-oxygen and hydrogen-air mixtures in a wide range of initial pressures and temperature levels, depending on the initial non-uniformity steepness. The limits of the regimes of reaction wave propagation depend upon the values of the spontaneous wave speed and the characteristic velocities of the problem. It is shown that one-step kinetics cannot reproduce either quantitative neither qualitative features of the ignition process in real gaseous mixtures because the difference between the induction time and the time when the exothermic reaction begins significantly affects the ignition, evolution, and coupling of the spontaneous reaction wave and the pressure wave, especially at lower temperatures. We show that all the regimes initiated by the temperature gradient occur for much shallower temperature gradients than predicted by a one-step model. The difference is very large for lower initial pressures and for slowly reacting mixtures. In this way the paper provides an answer to questions, important in practice, about the ignition energy, its distribution, and the scale of the initial nonuniformity required for ignition in one or another regime of combustion wave propagation.

  5. Importance of Reaction Mechanisms and Deformation on Gold Mineralisation

    NASA Astrophysics Data System (ADS)

    Pearce, M. A.; Hough, R.; Cleverley, J. S.

    2012-12-01

    Gold deposits are often associated with quartz and carbonate veining indicating mineralisation occurred during deformation and fluid flow. Investigation of several greenstone hosted deposits from Western Australia has shown that gold mineralisation in rocks that contain veins is often located in the wall rock not the veins themselves. This suggests that key processes are occurring in the wall rock causing the gold to precipitate from the fluid that carried it into the rocks. Continued reactions and deposition of gold demand that permeability is created and maintained in the host rocks. Microstructures are used to decipher the reactions that occurred in response to the gold-bearing fluid and to investigate the mechanisms of permeability generation in the host rocks. We present quantitative electron back-scatter diffraction data combined with spatially referenced major and trace-element chemistry to infer the reaction mechanisms active during fluid-rock interaction which potentially lead to the gold mineralisation. Data are presented showing the chemically driven recrystallisation of large (several mm) calcite grains to produce iron rich carbonates. Recystallisation occurs by nucleation of new grains which are in low energy orientations (epitactic and twin orientations) with respect to the host. The iron is sourced from large biotite and ilmenite grains which are breaking down as a result of the carbonate metasomatism to form fine grained polycrystalline aggregates. Biotite is reacting to muscovite and gold grains are found associated with this reaction (inter-mingled with the two micas and at the reaction fronts between them). In these samples, the importance of brittle deformation seems to be limited to vein creation allowing large volumes of fluid into the rock in the first place. There is evidence for limited crystal plastic deformation in the older carbonate and biotite grains. Reactions fronts in the biotite are perpendicular to the grain boundaries (as opposed to along the cleavage planes) so it is inferred that grain boundary fluid transport is more important than fracturing on the grain scale. Therefore, the grain-size reduction caused by the chemically induced recrystallisation is potentially of important in speeding up fluid transport through the rock. Gold depositions could be caused by a number of mechanisms including creation of space due to local volume loss during reactions or redox reactions that occur when iron is removed from ilmenite and biotite and incorporated into the carbonates.Biotite (pink) reacting to muscovite (red) and chlorite (green/blue) and associated gold mineralisation (black)

  6. Theory of chemical reaction dynamics. Volume 3

    SciTech Connect

    Baer, M.

    1985-01-01

    This book examines some of the basic principles behind chemical reaction kinetics. Topics considered include the classical trajectory approach to reactive scattering; periodic orbits and theory of reactive scattering; and semiclassical reactive scattering.

  7. Deterministic Function Computation with Chemical Reaction Networks

    E-print Network

    Doty, David

    systems, "wet robots", smart drugs, etc. #12;4 Chemical Reaction Networks (CRN) syntax: we use only came free with my toilet brush! #12;3 Cells are smart: controlled by signaling and regulatory networks

  8. FAST ELEMENTARY STEPS IN CHEMICAL REACTION MECHANSIMS

    Microsoft Academic Search

    M. Eigen

    1963-01-01

    A review is presented of studies of fast chemical reaction steps which ; were studied using various relaxation techniques. These studies include ligand ; substitution in metal complexes, proton transfer, and enzymatic hydrolysis. ; (D.L.C.);

  9. Concerted reactions of polynuclear metalloenzymes and their functional chemical models

    NASA Astrophysics Data System (ADS)

    Dzhabiev, T. S.; Shilov, A. E.

    2011-03-01

    The mechanisms of the many-electron oxidation of water by a chemical model of the manganese oxidase cofactor in photosynthesis photosystem II (manganese(IV) clusters) and nitrogen reduction in chemical models of nitrogenase cofactor (vanadium(II) and molybdenum(III) clusters) were considered. The hypothesis was suggested according to which polynuclear enzyme cofactors and their functional chemical models performed two important functions, catalyzed noncomplementary processes and effected many-substrate concerted reactions with decreased activation energies.

  10. Chemical kinetic reaction mechanism for the combustion of propane

    NASA Technical Reports Server (NTRS)

    Jachimowski, C. J.

    1984-01-01

    A detailed chemical kinetic reaction mechanism for the combustion of propane is presented and discussed. The mechanism consists of 27 chemical species and 83 elementary chemical reactions. Ignition and combustion data as determined in shock tube studies were used to evaluate the mechanism. Numerical simulation of the shock tube experiments showed that the kinetic behavior predicted by the mechanism for stoichiometric mixtures is in good agrement with the experimental results over the entire temperature range examined (1150-2600K). Sensitivity and theoretical studies carried out using the mechanism revealed that hydrocarbon reactions which are involved in the formation of the HO2 radical and the H2O2 molecule are very important in the mechanism and that the observed nonlinear behavior of ignition delay time with decreasing temperature can be interpreted in terms of the increased importance of the HO2 and H2O2 reactions at the lower temperatures.

  11. Chemical Principles Revisited: Annotating Reaction Equations.

    ERIC Educational Resources Information Center

    Tykodi, R. J.

    1987-01-01

    Urges chemistry teachers to have students annotate the chemical reactions in aqueous-solutions that they see in their textbooks and witness in the laboratory. Suggests this will help students recognize the reaction type more readily. Examples are given for gas formation, precipitate formation, redox interaction, acid-base interaction, and…

  12. Models for Multi-Specie Chemical Reactions Using Polynomial Stochastic Hybrid Systems

    E-print Network

    Hespanha, João Pedro

    Models for Multi-Specie Chemical Reactions Using Polynomial Stochastic Hybrid Systems Abhyudai for chemical reactions is presented. This is done by representing the population of various species involved in a chemical reaction as the continuous state of a polynomial Stochastic Hybrid System (pSHS). An important

  13. Grad's distribution functions in the kinetic equations for a chemical reaction

    E-print Network

    Spiga, Giampiero

    Grad's distribution functions in the kinetic equations for a chemical reaction Marzia Bisi, Maria of four species undergoing a bimolecular reversible chemical reaction, along with all possible elastic] and Prigogine-Xhrouet [2], kinetic approaches to chemical reactions in a gas have gained interest and importance

  14. Quantum Chemical Approach to Estimating the Thermodynamics of Metabolic Reactions

    NASA Astrophysics Data System (ADS)

    Jinich, Adrian; Rappoport, Dmitrij; Dunn, Ian; Sanchez-Lengeling, Benjamin; Olivares-Amaya, Roberto; Noor, Elad; Even, Arren Bar; Aspuru-Guzik, Alán

    2014-11-01

    Thermodynamics plays an increasingly important role in modeling and engineering metabolism. We present the first nonempirical computational method for estimating standard Gibbs reaction energies of metabolic reactions based on quantum chemistry, which can help fill in the gaps in the existing thermodynamic data. When applied to a test set of reactions from core metabolism, the quantum chemical approach is comparable in accuracy to group contribution methods for isomerization and group transfer reactions and for reactions not including multiply charged anions. The errors in standard Gibbs reaction energy estimates are correlated with the charges of the participating molecules. The quantum chemical approach is amenable to systematic improvements and holds potential for providing thermodynamic data for all of metabolism.

  15. Controlling chemical reactions of a single particle

    E-print Network

    Lothar Ratschbacher; Christoph Zipkes; Carlo Sias; Michael Köhl

    2012-09-26

    The control of chemical reactions is a recurring theme in physics and chemistry. Traditionally, chemical reactions have been investigated by tuning thermodynamic parameters, such as temperature or pressure. More recently, physical methods such as laser or magnetic field control have emerged to provide completely new experimental possibilities, in particular in the realm of cold collisions. The control of reaction pathways is also a critical component to implement molecular quantum information processing. For these undertakings, single particles provide a clean and well-controlled experimental system. Here, we report on the experimental tuning of the exchange reaction rates of a single trapped ion with ultracold neutral atoms by exerting control over both their quantum states. We observe the influence of the hyperfine interaction on chemical reaction rates and branching ratios, and monitor the kinematics of the reaction products. These investigations advance chemistry with single trapped particles towards achieving quantum-limited control of chemical reactions and indicate limits for buffer gas cooling of single ion clocks.

  16. Modeling of turbulent chemical reaction

    NASA Technical Reports Server (NTRS)

    Chen, J.-Y.

    1995-01-01

    Viewgraphs are presented on modeling turbulent reacting flows, regimes of turbulent combustion, regimes of premixed and regimes of non-premixed turbulent combustion, chemical closure models, flamelet model, conditional moment closure (CMC), NO(x) emissions from turbulent H2 jet flames, probability density function (PDF), departures from chemical equilibrium, mixing models for PDF methods, comparison of predicted and measured H2O mass fractions in turbulent nonpremixed jet flames, experimental evidence of preferential diffusion in turbulent jet flames, and computation of turbulent reacting flows.

  17. Chemical Reactions in Supercritical Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Wai, Chien M.; Hunt, Fred; Ji, Min; Chen, Xiaoyuan

    1998-12-01

    Utilizing supercritical fluids as environmentally benign solvents for chemical synthesis is one of the new approaches in the "greening" of chemistry. Carbon dioxide is the most widely used gas for supercritical fluid studies because of its moderate critical constants, nontoxic nature, and availability in pure form. One unique property of supercritical carbon dioxide (sc-CO2) is its high solubility for fluorinated compounds. Thus sc-CO2 can be used to replace Freons that are conventionally used as solvents for synthesis of perfluoro-polymers. Another property of sc-CO2 is its miscibility with gases such as H2. Heterogeneous reactions involving these gases may become homogeneous reactions in sc-CO2. Reactions in sc-CO2 may offer several advantages including controlling phase behavior and products, increasing speed of reactions, and obtaining specific reaction channels. This paper describes the following nine types of chemical reactions reported in the literature utilizing sc-CO2 as a solvent to illustrate the unique properties of the supercritical fluid reaction systems: (i) hydrogenation and hydroformylation, (ii) synthesis of organometallic compounds, (iii) metal chelation and extraction, (iv) preparation of inorganic nanoparticles, (v) stereo-selectivity of lipase-catalyzed reactions, (vi) asymmetric catalytic hydrogenation, (vii) polymerization, (viii) Diels-Alder reaction, and (ix) free radical reactions.

  18. Neutral theory of chemical reaction networks

    E-print Network

    Lee, Sang Hoon; Holme, Petter; Kim, Beom Jun; Minnhagen, Petter

    2011-01-01

    To what extent do the characteristic features of a chemical reaction network reflect its purpose and function? In general, one argues that correlations between specific features and specific functions are the key to understanding a complex structure. Yet specific features may sometimes be neutral and uncorrelated with any system-specific purpose, function, or causal chain. Such neutral features are caused by chance and randomness. Here we compare two classes of chemical networks: one that has been subject to biological evolution (the chemical reaction network of the metabolism in living cells) and one that has not (the atmospheric planetary chemical reaction networks). Their degree distributions are shown to share the very same neutral system-independent features. The shape of the broad distributions is to large extent controlled by a single parameter, the network size. From this perspective, there is little difference between atmospheric and metabolic networks; they are just different sizes of the same rando...

  19. Laboratory Studies of Heterogeneous Chemical Processes of Atmospheric Importance

    NASA Technical Reports Server (NTRS)

    Molina, Mario J.

    2004-01-01

    The objective of this study is to conduct measurements of chemical kinetics parameters for heterogeneous reactions of importance in the stratosphere and the troposphere. It involves the elucidation of the mechanism of the interaction of HCl vapor with ice surfaces, which is the first step in the heterogeneous chlorine activation processes, as well as the investigation of the atmospheric oxidation mechanism of soot particles emitted by biomass and fossil fuels. The techniques being employed include turbulent flow-chemical ionization mass spectrometry and optical ellipsometry, among others.

  20. Entropy generation in a chemical reaction

    E-print Network

    E. N. Miranda

    2012-08-10

    Entropy generation in a chemical reaction is analyzed without using the general formalism of non-equilibrium thermodynamics at a level adequate for advanced undergraduates. In a first approach to the problem, the phenomenological kinetic equation of an elementary first order reaction is used to show that entropy production is always positive. A second approach assumes that the reaction is near equilibrium to prove that the entropy generated is always greater than zero, without any reference to the kinetics of the reaction. Finally, it is shown that entropy generation is related to fluctuations in the number of particles at equilibrium, i.e. it is associated to a microscopic process.

  1. Entropy generation in a chemical reaction

    E-print Network

    Miranda, E N

    2012-01-01

    Entropy generation in a chemical reaction is analyzed without using the general formalism of non-equilibrium thermodynamics at a level adequate for advanced undergraduates. In a first approach to the problem, the phenomenological kinetic equation of an elementary first order reaction is used to show that entropy production is always positive. A second approach assumes that the reaction is near equilibrium to prove that the entropy generated is always greater than zero, without any reference to the kinetics of the reaction. Finally, it is shown that entropy generation is related to fluctuations in the number of particles at equilibrium, i.e. it is associated to a microscopic process.

  2. Plasmonic smart dust for probing local chemical reactions.

    PubMed

    Tittl, Andreas; Yin, Xinghui; Giessen, Harald; Tian, Xiang-Dong; Tian, Zhong-Qun; Kremers, Christian; Chigrin, Dmitry N; Liu, Na

    2013-04-10

    Locally probing chemical reactions or catalytic processes on surfaces under realistic reaction conditions has remained one of the main challenges in materials science and heterogeneous catalysis. Where conventional surface interrogation techniques usually require high-vacuum conditions or ensemble average measurements, plasmonic nanoparticles excel in extreme light focusing and can produce highly confined electromagnetic fields in subwavelength volumes without the need for complex near-field microscopes. Here, we demonstrate an all-optical probing technique based on plasmonic smart dust for monitoring local chemical reactions in real time. The silica shell-isolated gold nanoparticles that form the smart dust can work as strong light concentrators and optically report subtle environmental changes at their pinning sites on the probed surface during reaction processes. As a model system, we investigate the hydrogen dissociation and subsequent uptake trajectory in palladium with both "dust-on-film" and "film-on-dust" platforms. Using time-resolved single particle measurements, we demonstrate that our technique can in situ encode chemical reaction information as optical signals for a variety of surface morphologies. The presented technique offers a unique scheme for real-time, label-free, and high-resolution probing of local reaction kinetics in a plethora of important chemical reactions on surfaces, paving the way toward the development of inexpensive and high-output reaction sensors for real-world applications. PMID:23458121

  3. A Synthetic Reaction Network: Chemical Amplification Using Nonequilibrium Autocatalytic Reactions Coupled in Time

    E-print Network

    Ismagilov, Rustem F.

    A Synthetic Reaction Network: Chemical Amplification Using Nonequilibrium Autocatalytic Reactions reaction network synthesized in a microfluidic device. This chemical network performs chemical 5000-fold by a reaction autocatalytic in Co2+ . The microfluidic network is used to maintain the two chemical reactions

  4. CONTINUOUS TIME MARKOV CHAIN MODELS FOR CHEMICAL REACTION NETWORKS

    E-print Network

    Anderson, David F.

    Chapter 1 CONTINUOUS TIME MARKOV CHAIN MODELS FOR CHEMICAL REACTION NETWORKS David F. Anderson@math.wisc.edu Abstract A reaction network is a chemical system involving multiple reactions and chemical species-05793 #12;2 the representation of the stochastic equation for chemical reaction net- works and, under what

  5. Stochastic thermodynamics of chemical reaction networks

    E-print Network

    Tim Schmiedl; Udo Seifert

    2006-12-19

    For chemical reaction networks described by a master equation, we define energy and entropy on a stochastic trajectory and develop a consistent nonequilibrium thermodynamic description along a single stochastic trajectory of reaction events. A first-law like energy balance relates internal energy, applied (chemical) work and dissipated heat for every single reaction. Entropy production along a single trajectory involves a sum over changes in the entropy of the network itself and the entropy of the medium. The latter is given by the exchanged heat identified through the first law. Total entropy production is constrained by an integral fluctuation theorem for networks arbitrarily driven by time-dependent rates and a detailed fluctuation theorem for networks in the steady state. Further exact relations like a generalized Jarzynski relation and a generalized Clausius inequality are discussed. We illustrate these results for a three-species cyclic reaction network which exhibits nonequilibrium steady states as well as transitions between different steady states.

  6. Chemical Memory Reactions Induced Bursting Dynamics in Gene Expression

    PubMed Central

    Tian, Tianhai

    2013-01-01

    Memory is a ubiquitous phenomenon in biological systems in which the present system state is not entirely determined by the current conditions but also depends on the time evolutionary path of the system. Specifically, many memorial phenomena are characterized by chemical memory reactions that may fire under particular system conditions. These conditional chemical reactions contradict to the extant stochastic approaches for modeling chemical kinetics and have increasingly posed significant challenges to mathematical modeling and computer simulation. To tackle the challenge, I proposed a novel theory consisting of the memory chemical master equations and memory stochastic simulation algorithm. A stochastic model for single-gene expression was proposed to illustrate the key function of memory reactions in inducing bursting dynamics of gene expression that has been observed in experiments recently. The importance of memory reactions has been further validated by the stochastic model of the p53-MDM2 core module. Simulations showed that memory reactions is a major mechanism for realizing both sustained oscillations of p53 protein numbers in single cells and damped oscillations over a population of cells. These successful applications of the memory modeling framework suggested that this innovative theory is an effective and powerful tool to study memory process and conditional chemical reactions in a wide range of complex biological systems. PMID:23349679

  7. Instantaneous Chemical Reactions in Benzene and Toluene

    E-print Network

    Allen, Herman Camp

    1905-06-07

    KU ScholarWorks | The University of Kansas Pre-1923 Dissertations and Theses Collection Instantaneous Chemical Reac- tions in Benzene and Toluene June 7th, 1905 by Herman Camp Allen This work was digitized by the Scholarly Communications program... Chemistry Allen, H.C. 1905 "Instantaneous reactions (chemical) in benzene and toluene". I ! B f O H B M I O A L REACTIONS IN Bt«2F;»F! AND TQLUBMB, Presented to the faculty of the University of Kansas in partial fulfillment of the requirements...

  8. Decrease of Entropy and Chemical Reactions

    E-print Network

    Yi-Fang Chang

    2008-07-01

    The chemical reactions are very complex, and include oscillation, condensation, catalyst and self-organization, etc. In these case changes of entropy may increase or decrease. The second law of thermodynamics is based on an isolated system and statistical independence. If fluctuations magnified due to internal interactions exist in the system, entropy will decrease possibly. In chemical reactions there are various internal interactions, so that some ordering processes with decrease of entropy are possible on an isolated system. For example, a simplifying Fokker-Planck equation is solved, and the hysteresis as limit cycle is discussed.

  9. Acceleration of chemical reaction by chaotic mixing

    E-print Network

    M. Chertkov; V. Lebedev

    2003-01-27

    Theory of fast binary chemical reaction, ${\\cal A}+{\\cal B}\\to{\\cal C}$, in a statistically stationary chaotic flow at large Schmidt number ${Sc}$ and large Damk\\"ohler number ${Da}$ is developed. For stoichiometric condition we identify subsequent stages of the chemical reaction. The first stage corresponds to the exponential decay, $\\propto\\exp(-\\lambda t)$ (where $\\lambda$ is the Lyapunov exponent of the flow), of the chemicals in the bulk part of the flow. The second and the third stages are related to the chemicals remaining in the boundary region. During the second stage the amounts of ${\\cal A}$ and ${\\cal B}$ decay $\\propto 1/\\sqrt{t}$, whereas the decay law during the third stage is exponential, $\\propto\\exp(-\\gamma t)$, where $\\gamma\\sim\\lambda/\\sqrt{Sc}$.

  10. Continuous Time Markov Chain Models for Chemical Reaction

    E-print Network

    Anderson, David F.

    Chapter 7 Continuous Time Markov Chain Models for Chemical Reaction Networks 7.1 Chemical reaction chemical reactions involving N chemical species, S1, . . . , SN , N i=1 ikSi N i=1 ikSi, k = 1, in Sec- tion 7.1.1 by developing the basic stochastic equations for chemical systems. Next, in Section 7

  11. Concordant Chemical Reaction Networks and the Species-Reaction Graph

    E-print Network

    Shinar, Guy

    2012-01-01

    In a recent paper it was shown that, for chemical reaction networks possessing a subtle structural property called concordance, dynamical behavior of a very circumscribed (and largely stable) kind is enforced, so long as the kinetics lies within the very broad and natural class of weakly monotonic kinetics. In particular, multiple equilibria are precluded, as are degenerate positive equilibria. Moreover, under certain circumstances, also related to concordance, all real eigenvalues associated with a positive equilibrium are negative. Although concordance of a reaction network can be decided by readily available computational means, we show here that, when a nondegenerate network's Species Reaction Graph satisfies certain mild conditions, concordance and its dynamical consequences are ensured. These conditions are weaker than earlier ones invoked to establish kinetic system injectivity, which, in turn, is just one ramication of network concordance. Because the Species Reaction Graph resembles pathway depiction...

  12. An Alternative to Gillespie's Algorithm for Simulating Chemical Reactions

    E-print Network

    Torino, Università di

    An Alternative to Gillespie's Algorithm for Simulating Chemical Reactions Roberto Barbuti, Andrea introduce a probabilistic algorithm for the simulation of chemical reactions, which can be used evolution of chemical reactive systems described by Gillespie. Moreover, we use our algorithm

  13. LIGAND: chemical database of enzyme reactions

    PubMed Central

    Goto, Susumu; Nishioka, Takaaki; Kanehisa, Minoru

    2000-01-01

    LIGAND is a composite database comprising three sections: ENZYME for the information of enzyme molecules and enzymatic reactions, COMPOUND for the information of metabolites and other chemical compounds, and REACTION for the collection of substrate–product relations. The current release includes 3390 enzymes, 5645 compounds and 5207 reactions. The database is indispensable for the reconstruction of metabolic pathways in the completely sequenced organisms. The LIGAND database can be accessed through the WWW (http://www.genome.ad.jp/dbget/ligand.html ) or may be downloaded by anonymous FTP (ftp://kegg.genome.ad.jp/molecules/ligand/ ). PMID:10592281

  14. 40 CFR 799.19 - Chemical imports and exports.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...2012-07-01 2012-07-01 false Chemical imports and exports. 799.19 Section...CONTINUED) IDENTIFICATION OF SPECIFIC CHEMICAL SUBSTANCE AND MIXTURE TESTING REQUIREMENTS General Provisions § 799.19 Chemical imports and exports. Persons...

  15. 40 CFR 799.19 - Chemical imports and exports.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 2014-07-01 false Chemical imports and exports. 799.19 Section...CONTINUED) IDENTIFICATION OF SPECIFIC CHEMICAL SUBSTANCE AND MIXTURE TESTING REQUIREMENTS General Provisions § 799.19 Chemical imports and exports. Persons...

  16. 40 CFR 799.19 - Chemical imports and exports.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 2013-07-01 false Chemical imports and exports. 799.19 Section...CONTINUED) IDENTIFICATION OF SPECIFIC CHEMICAL SUBSTANCE AND MIXTURE TESTING REQUIREMENTS General Provisions § 799.19 Chemical imports and exports. Persons...

  17. Classification of Chemical Reactions: Stages of Expertise

    ERIC Educational Resources Information Center

    Stains, Marilyne; Talanquer, Vicente

    2008-01-01

    In this study we explore the strategies that undergraduate and graduate chemistry students use when engaged in classification tasks involving symbolic and microscopic (particulate) representations of different chemical reactions. We were specifically interested in characterizing the basic features to which students pay attention when classifying…

  18. Regenerative fuel cell with chemical reactions

    Microsoft Academic Search

    P. B. L. Chaurasia; Yuji Ando; Tadayoshi Tanaka

    2003-01-01

    The function of fuel cells largely depends upon catalytic electrodes which accomplish a chemical reaction to convert fuel into electric energy. For this purpose, a study has been conducted on different catalysts prepared from various precursors and tested in the fuel cells for power generation under identical conditions. A new precursor has been identified to prepare the catalysts, giving encouraging

  19. Computer Animation of a Chemical Reaction.

    ERIC Educational Resources Information Center

    Eaker, Charles W.; Jacobs, Edwin L.

    1982-01-01

    Taking a prototype chemical reaction (molecular hydrogen plus hydrogen atom), constructs an accurate semiempirical, generalized diatomics-in-molecules potential energy surface, calculates motions of these atoms on this surface using REACTS trajectory program, and presents results as moving picture on a microcomputer graphics system. Provides…

  20. Chemical reactions in turbulent mixing flows

    NASA Astrophysics Data System (ADS)

    Dimotakis, Paul E.; Leonard, Anthony

    1993-07-01

    In the course of this research we have conducted investigations of turbulent mixing, chemical reaction, and combustion processes in turbulent, subsonic, and supersonic flows. The program was comprised of several parts: an experimental effort, a theoretical and numerical simulation effort, and a development of instrumentation and diagnostics; an upgrade of flow and combustion facilities; and the development of data-acquisition sub-systems. We have carried out a series of theoretical and experimental studies of turbulent mixing in two well-defined, fundamentally important flow fields: free-shear layers and axisymmetric jets. To elucidate molecular transport effects, experiments and theory have dealt with both reacting and non-reacting flows of liquids and gases in fully-developed turbulent flows. A criterion for fully-developed turbulence was recently developed. The computational studies are, at present, focused at fundamental formulation and implementation issues pertaining to the simulation of both compressible and incompressible flows characterized by strong fronts, such as shock waves and flames. In our diagnostic development efforts we have improved the signal-to-noise ratio of flow images, in both gas- and liquid-phase flows, as well as continued with the development of data-acquisition electronics to meet very high-speed, high-volume data requirements; the acquisition of single, or pairs, of two-dimensional images in rapid succession; and the acquisition of data from arrays of supersonic flow sensors.

  1. Continuous time Markov chain models for chemical reaction networks

    E-print Network

    Kurtz, Tom

    Continuous time Markov chain models for chemical reaction networks David F. Anderson Departments classifications: 60J27, 60J28, 60J80, 60F17, 80A30, 92C40 Keywords: Reaction network, Markov chain, law of mass Abstract A reaction network is a chemical system involving multiple reactions and chemical species

  2. Monotonicity and convergence in chemical reaction networks Patrick De Leenheer

    E-print Network

    Sontag, Eduardo

    Monotonicity and convergence in chemical reaction networks Patrick De Leenheer Dep. of Mathematics- of chemical reaction networks. The results do not assume any particular form for the kinetics of the reactions of the qualitative behavior of chemical reaction networks is an area of growing interest, especially in light

  3. Inferring Chemical Reaction Patterns Using Rule Composition in Graph Grammars

    E-print Network

    Flamm, Christoph

    Inferring Chemical Reaction Patterns Using Rule Composition in Graph Grammars Jakob Lykke Andersen1:studla@bioinf.uni-leipzig.de; Corresponding author Abstract Background: Modeling molecules as undirected graphs and chemical reactions, to summarize several subsequent reactions into a single composite chemical reaction. Results: We introduce

  4. Steady detonation problem for slow and fast chemical reactions

    E-print Network

    Ceragioli, Francesca

    Steady detonation problem for slow and fast chemical reactions F. Conforto1 , M. Groppi2 , R chemical reaction are discussed. The former consists in a system of balance laws for the case of a chemical is a system of conser- vation laws for the case of short chemical relaxation time (fast reaction). After

  5. Chemical computing with reaction-diffusion processes.

    PubMed

    Gorecki, J; Gizynski, K; Guzowski, J; Gorecka, J N; Garstecki, P; Gruenert, G; Dittrich, P

    2015-07-28

    Chemical reactions are responsible for information processing in living organisms. It is believed that the basic features of biological computing activity are reflected by a reaction-diffusion medium. We illustrate the ideas of chemical information processing considering the Belousov-Zhabotinsky (BZ) reaction and its photosensitive variant. The computational universality of information processing is demonstrated. For different methods of information coding constructions of the simplest signal processing devices are described. The function performed by a particular device is determined by the geometrical structure of oscillatory (or of excitable) and non-excitable regions of the medium. In a living organism, the brain is created as a self-grown structure of interacting nonlinear elements and reaches its functionality as the result of learning. We discuss whether such a strategy can be adopted for generation of chemical information processing devices. Recent studies have shown that lipid-covered droplets containing solution of reagents of BZ reaction can be transported by a flowing oil. Therefore, structures of droplets can be spontaneously formed at specific non-equilibrium conditions, for example forced by flows in a microfluidic reactor. We describe how to introduce information to a droplet structure, track the information flow inside it and optimize medium evolution to achieve the maximum reliability. Applications of droplet structures for classification tasks are discussed. PMID:26078345

  6. Chemical reactions in reverse micelle systems

    DOEpatents

    Matson, Dean W. (Kennewick, WA); Fulton, John L. (Richland, WA); Smith, Richard D. (Richland, WA); Consani, Keith A. (Richland, WA)

    1993-08-24

    This invention is directed to conducting chemical reactions in reverse micelle or microemulsion systems comprising a substantially discontinuous phase including a polar fluid, typically an aqueous fluid, and a microemulsion promoter, typically a surfactant, for facilitating the formation of reverse micelles in the system. The system further includes a substantially continuous phase including a non-polar or low-polarity fluid material which is a gas under standard temperature and pressure and has a critical density, and which is generally a water-insoluble fluid in a near critical or supercritical state. Thus, the microemulsion system is maintained at a pressure and temperature such that the density of the non-polar or low-polarity fluid exceeds the critical density thereof. The method of carrying out chemical reactions generally comprises forming a first reverse micelle system including an aqueous fluid including reverse micelles in a water-insoluble fluid in the supercritical state. Then, a first reactant is introduced into the first reverse micelle system, and a chemical reaction is carried out with the first reactant to form a reaction product. In general, the first reactant can be incorporated into, and the product formed in, the reverse micelles. A second reactant can also be incorporated in the first reverse micelle system which is capable of reacting with the first reactant to form a product.

  7. Polymer Reaction Engineering Laboratory Chemical and Biomolecular Engineering

    E-print Network

    Choi, Kyu Yong

    Transporting chemicals Fume hoods and ventilation Refrigerators Incompatible chemicals The followingPolymer Reaction Engineering Laboratory Chemical and Biomolecular Engineering University of the chemicals involved. Know the safety precautions and emergency procedures that protect you from those hazards

  8. Quantum Theory of Fast Chemical Reactions

    Microsoft Academic Search

    John C. Light

    2007-01-01

    The aims of the research under this grant were to develop a;\\u000atheoretical understanding and;\\u000apredictive abiility for a variety of processes occurring in the;\\u000agas phase.;\\u000aThese included bimolecular chemical exchange reactions,;\\u000aphotodissociation,;\\u000apredissociation resonances, unimolecular reactions and recombination;\\u000areactions. In general we assumed a knowledge, from quantum chemistry,;\\u000aof the interactions of the atoms and molecular fragments involved.;

  9. Researches on Preliminary Chemical Reactions in Spark-Ignition Engines

    NASA Technical Reports Server (NTRS)

    Muehlner, E.

    1943-01-01

    Chemical reactions can demonstrably occur in a fuel-air mixture compressed in the working cylinder of an Otto-cycle (spark ignition) internal-combustion engine even before the charge is ignited by the flame proceeding from the sparking plug. These are the so-called "prelinminary reactions" ("pre-flame" combustion or oxidation), and an exact knowledge of their characteristic development is of great importance for a correct appreciation of the phenomena of engine-knock (detonation), and consequently for its avoidance. Such reactions can be studied either in a working engine cylinder or in a combustion bomb. The first method necessitates a complicated experimental technique, while the second has the disadvantage of enabling only a single reaction to be studied at one time. Consequently, a new series of experiments was inaugurated, conducted in a motored (externally-driven) experimental engine of mixture-compression type, without ignition, the resulting preliminary reactions being detectable and measurable thermometrically.

  10. Quantum Theory of Chemical Reaction Dynamics.

    NASA Astrophysics Data System (ADS)

    Zhao, Meishan

    The generalized Newton variational principle is extended to treat chemical reactions with nonzero total angular momentum J, and it is applied to various chemical reactions with J = 0 to 20. Chapter 1 reviews the basic theory and discusses the evaluation of nonzero-J matrix elements. Chapters 2-5 report extensive quantum mechanical calculations on the reaction H + p-H_2 to o-H_2 + H. Chapter 2 reports vibrational branching ratios. Chapter 3 reports probabilities and partial cross sections, which are compared to corresponding quantities calculated by the quasiclassical trajectory method. Chapter 4 presents converged quantum mechanical state-to-state cross sections. The converged vibrational branching ratio is in good agreement with recent experiments but the rotational distribution is not. Chapter 5 reports converged quantum mechanical calculations of resonances and time delays for total angular momentum 0, 1, and 4. Chapter 4 compares the results of classical simulations to accurate quantum studies for the reaction D + H _2 to HD + H. Chapter 7 presents accurate state-to-state transition probabilities and delay times for this reaction. Chapter 8 reports fully converged quantum mechanical transition probabilities for the F + H_2 to HF + H reaction. Chapter 9 presents calculations of state-to-state partial reaction cross sections in H + D_2 to HD + D collisions. The results are compared to quasiclassical trajectory calculations to test the classical simulation method. In chapter 10 a new method for constructing efficient basis functions for {cal L}^2 variational calculations of quantum mechanical rearrangements is presented and tested.

  11. Semiclassical approaches to controlling chemical reaction dynamics

    E-print Network

    Hiroshi Fujisaki; Yoshiaki Teranishi; Alexey Kondorskiy; Hiroki Nakamura

    2003-02-04

    We propose to use semiclassical methods to treat laser control problems of chemical reaction dynamics. Our basic strategy is as follows: Laser-driven chemical reactions are considered to consist of two processes. One is the wavepacket propagation on an adiabatic potential energy surface (PES), and the other is the electronic transition between PES's. Because the latter process is mathematically equivalent to nonadiabatic transitions between Floquet (dressed) states, we can control such a process using the semiclassical Zhu-Nakamura theory for nonadiabatic transitions. For the former process, we incorporate semiclassical propagation methods such as the Herman-Kluk propagator into optimization procedures like optimal control theory. We show some numerical examples for our strategies. We also develop a semiclassical direct algorithm to treat the adiabatic propagation and nonadiabatic transitions as a whole.

  12. Chemical reaction systems with toric steady states

    E-print Network

    Millan, Mercedes Perez; Shiu, Anne; Conradi, Carsten

    2011-01-01

    Mass-action chemical reaction systems are frequently used in Computational Biology. The corresponding polynomial dynamical systems are often large, consisting of tens or even hundreds of ordinary differential equations, and poorly parameterized (due to noisy measurement data and a small number of data points and repetitions). Therefore, it is often difficult to establish the existence of (positive) steady states or to determine whether more complicated phenomena such as multistationarity exist. If, however, the steady state ideal of the system is a binomial ideal, then we show that these questions can be answered easily. The focus of this work is on systems with this property, and we say that such systems have toric steady states. Our main result gives sufficient conditions for a chemical reaction system to have toric steady states. Furthermore, we analyze the capacity of such a system to exhibit positive steady states and multistationarity. Examples of systems with toric steady states include weakly-reversib...

  13. Photochemical reactions of anthropogenic chemicals in seawater

    SciTech Connect

    Toole, A.P.; Crosby, D.G. (Univ. of California, Davis (USA))

    1988-09-01

    Sunlight-driven, photochemical reactions can be a major degradative force for anthropogenic organic compounds in the aquatic environment. Chlorinated phenols, various classes of pesticides, and polycyclic aromatic hydrocarbons are among some examples of the compounds shown to be degraded by sunlight. Most environmental photochemistry has been studied in fresh water, despite the fact that the oceans cover more than 70% of the earths surface and receive large inputs of anthropogenic chemicals via atmospheric transport, runoff, and coastal outfalls. This fact, along with increasing pressure for ocean waste disposal as land options dwindle, present a need for information on the photochemical reactions of anthropogenic organic chemicals in seawater. Several probable seawater pollutants were selected as probes for studying photochemical reactions including, 2-nitrotoluene, 4-nitrotoluene, styrene, 4,5-dichloroguaiacol, 4,5,6-trichloroguaiacol and tetrachloroguaiacol. Dilute solutions of each probe were prepared in buffered (pH 8), distilled water (DW), synthetic seawater (SSW) and natural seawater (NSW), then irradiated in a temperature-controlled photoreactor fitted with a General Electric F40BL fluorescent lamp to simulate sunlight. Samples were taken at regular intervals, concentrated using solid phase extraction techniques and analyzed by gas chromatography. Photolysis rates were determined assuming first, or pseudo-first, order kinetics. Photoproducts were identified by gas chromatography;mass spectrometry and confirmed by comparison to standards when available. By determining rates in DW containing selected components of SSW, at SSW concentrations, the inorganic compounds mediating the photochemical reactions in seawater could be determined.

  14. Density functional study of chemical reaction equilibrium for dimerization reactions in slit and cylindrical nanopores

    E-print Network

    Lisal, Martin

    Density functional study of chemical reaction equilibrium for dimerization reactions in slit a theoretical study of the effects of confinement on chemical reaction equilibrium in slit and cylindrical equilibrium, for which much less is known. The behavior of chemical reactions in confinement spans a wide

  15. Multiscale stochastic simulations of chemical reactions with regulated scale separation

    SciTech Connect

    Koumoutsakos, Petros, E-mail: petros@ethz.ch [Chair of Computational Science, Clausiusstrasse 33, ETH Zurich, CH-8092 (Switzerland)] [Chair of Computational Science, Clausiusstrasse 33, ETH Zurich, CH-8092 (Switzerland); Feigelman, Justin [Chair of Computational Science, Clausiusstrasse 33, ETH Zurich, CH-8092 (Switzerland)] [Chair of Computational Science, Clausiusstrasse 33, ETH Zurich, CH-8092 (Switzerland)

    2013-07-01

    We present a coupling of multiscale frameworks with accelerated stochastic simulation algorithms for systems of chemical reactions with disparate propensities. The algorithms regulate the propensities of the fast and slow reactions of the system, using alternating micro and macro sub-steps simulated with accelerated algorithms such as ? and R-leaping. The proposed algorithms are shown to provide significant speedups in simulations of stiff systems of chemical reactions with a trade-off in accuracy as controlled by a regulating parameter. More importantly, the error of the methods exhibits a cutoff phenomenon that allows for optimal parameter choices. Numerical experiments demonstrate that hybrid algorithms involving accelerated stochastic simulations can be, in certain cases, more accurate while faster, than their corresponding stochastic simulation algorithm counterparts.

  16. The role of chemical reactions in the Chernobyl accident

    NASA Astrophysics Data System (ADS)

    Grishanin, E. I.

    2010-12-01

    It is shown that chemical reactions played an essential role in the Chernobyl accident at all of its stages. It is important that the reactor before the explosion was at maximal xenon poisoning, and its reactivity, apparently, was not destroyed by the explosion. The reactivity release due to decay of Xe-235 on the second day after the explosion led to a reactor power of 80-110 MW. Owing to this power, the chemical reactions of reduction of uranium, plutonium, and other metals at a temperature of about 2000°C occurred in the core. The yield of fission products thus sharply increased. Uranium and other metals flew down in the bottom water communications and rooms. After reduction of the uranium and its separation from the graphite, the chain reaction stopped, the temperature of the core decreased, and the activity yield stopped.

  17. Computed potential energy surfaces for chemical reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Levin, Eugene

    1993-01-01

    A new global potential energy surface (PES) is being generated for O(P-3) + H2 yields OH + H. This surface is being fit using the rotated Morse oscillator method, which was used to fit the previous POL-CI surface. The new surface is expected to be more accurate and also includes a much more complete sampling of bent geometries. A new study has been undertaken of the reaction N + O2 yields NO + O. The new studies have focused on the region of the surface near a possible minimum corresponding to the peroxy form of NOO. A large portion of the PES for this second reaction has been mapped out. Since state to state cross sections for the reaction are important in the chemistry of high temperature air, these studies will probably be extended to permit generation of a new global potential for reaction.

  18. CHAPTER 9. CHEMICAL KINETICS In the following chapters we will present various chemical reaction

    E-print Network

    Jacob, Daniel J.

    AND CHEMICAL EQUILIBRIA Reactions are re155 CHAPTER 9. CHEMICAL KINETICS In the following chapters we will present various chemical reaction mechanisms controlling the abundance of stratospheric ozone, the oxidizing power of the atmosphere

  19. Model Reduction of Chemical Reaction Systems using Elimination

    E-print Network

    Paris-Sud XI, Université de

    Model Reduction of Chemical Reaction Systems using Elimination Fran¸cois Boulier, Marc Lefranc for parametric ordinary differential systems arising from chemical reaction systems. In this paper, we focus is different from those of Henri-Micha¨elis-Menten and Briggs-Haldane. 1. Introduction Chemical reaction

  20. GRAPH THEORETIC APPROACHES TO INJECTIVITY IN CHEMICAL REACTION SYSTEMS

    E-print Network

    Craciun, Gheorghe

    GRAPH THEORETIC APPROACHES TO INJECTIVITY IN CHEMICAL REACTION SYSTEMS MURAD BANAJI AND GHEORGHE algebraic and graph theoretic conditions for injectivity of chemical reaction systems. After developing the possibility of multiple equilibria in the systems in question. Key words. Chemical reactions; Injectivity; SR

  1. Chemical Reaction Dynamics accompanying Electron-Transfer Osamu SUGINO

    E-print Network

    Katsumoto, Shingo

    Chemical Reaction Dynamics accompanying Electron-Transfer Osamu SUGINO Institute for Solid State Physics, the University of Tokyo 5-1-5 Kashiwanoha, Chiba 277-8581 1. Introduction Many chemical reactions and the dynamics goes nonadiabatically. The former appears typically in chemical reactions that accompany electron

  2. Gamma and the chemical reaction model: fteen years after?

    E-print Network

    Fradet, Pascal

    Gamma and the chemical reaction model: fteen years after? Jean-Pierre Ban^atre1, Pascal Fradet2 the formalism is to describe computation as a form of chemical reaction on a collection of individual pieces on unexpected applications of the chemical reaction model, showing that this paradigm has been a source

  3. Asymptotic behaviour of reversible chemical reaction-diffusion equations

    E-print Network

    Paris-Sud XI, Université de

    Asymptotic behaviour of reversible chemical reaction-diffusion equations Ivan Gentil and Boguslaw chemical reaction-diffusion equations with the same diffusion. In particular we prove the optimal rate40, 35A05, 35F25 1 Introduction The self-ionization of water is the chemical reaction in which two

  4. P MATRIX PROPERTIES, INJECTIVITY AND STABILITY IN CHEMICAL REACTION SYSTEMS

    E-print Network

    Banaji,. Murad

    P MATRIX PROPERTIES, INJECTIVITY AND STABILITY IN CHEMICAL REACTION SYSTEMS MURAD BANAJI§, PETE. Chemical reactions; P matrices; Injectivity; Stability; Mass action AMS subject classifications. 80A30; 15A48; 34D30 1. Introduction. In this paper we will study chemical reaction systems, and systems derived

  5. Reasoning and Representation: the Sketching of Organic Chemical Reaction Mechanisms

    E-print Network

    Marchese, Francis

    Reasoning and Representation: the Sketching of Organic Chemical Reaction Mechanisms Position paper of sketching chemical reaction mechanisms in order to reason-out the structural transformations that convert. The general chemical reaction patterns of oxidation-reduction, functional group transfer, hydrolysis

  6. Thermal Coefficients and Heat Capacities in Systems with Chemical Reaction

    E-print Network

    Matías, Manuel A.

    Thermal Coefficients and Heat Capacities in Systems with Chemical Reaction The Le Chatelier of the study of the equilib- rium states in chemical reactions is based much on the for- mulation of empirical and rigorous basis for the effect of external pertur- bations on a chemical reaction. Namely, the basis

  7. CANARDS, BLACK SWANS AND CONTROL OF CHEMICAL REACTIONS Vladimir Sobolev

    E-print Network

    CANARDS, BLACK SWANS AND CONTROL OF CHEMICAL REACTIONS By Vladimir Sobolev and Elena Shchepakina: 612-626-7370 URL: http://www.ima.umn.edu #12;Canards, Black Swans and Control of Chemical Reactions V. The sense of criticality here is as follows. The critical regime corresponds to chemical reaction separating

  8. Chemical Reaction Systems, Computer Algebra and Systems Biology

    E-print Network

    Boyer, Edmond

    Chemical Reaction Systems, Computer Algebra and Systems Biology Fran¸cois Boulier1 , Fran dynam- ics of chemical reaction systems. This cooperation led us to efficient algorithms for building the corre- sponding MAPLE packages. Chemical reaction systems provide a general setting for modeling

  9. Molecular dynamics study of fracture accompanied by chemical reaction

    E-print Network

    Krivtsov, Anton M.

    Molecular dynamics study of fracture accompanied by chemical reaction Anton M. Krivtsov akrivtsov of the chemical reaction (oxidation) on the fracture scenario is investigated. Fracture process for the specimens applications the fracture is closely connected with chemical reactions. In particular, for MEMS made from

  10. Programmability of Chemical Reaction Matthew Cook, David Soloveichik, Erik Winfree,

    E-print Network

    Winfree, Erik

    Programmability of Chemical Reaction Networks Matthew Cook, David Soloveichik, Erik Winfree cells we study Stochastic Chemical Reaction Networks (SCRNs), a for- mal model that considers a set of chemical reactions acting on a finite num- ber of molecules in a well-stirred solution according

  11. Reconstructing Chemical Reaction Networks: Data Mining meets System Identification

    E-print Network

    Ramakrishnan, Naren

    Reconstructing Chemical Reaction Networks: Data Mining meets System Identification Yong Ju Cho typically begins with a chemical reaction network (CRN), which is then converted to a set of simul- taneous in any domain where chemical reaction systems form the origins of the underlying numerical model (ODE

  12. Sensitivity of chemical reaction networks: a structural approach.

    E-print Network

    Fiedler, Bernold

    Sensitivity of chemical reaction networks: a structural approach. 2. Regular monomolecular systems to perturbations of reaction rates in chemical reaction networks. Strong motivation for our study comes from recent For the deceptively innocent case of monomolecular reactions, only, we embark on a systematic mathematical analysis

  13. A kinetic mechanism inducing oscillations in simple chemical reactions networks

    E-print Network

    Altafini, Claudio

    A kinetic mechanism inducing oscillations in simple chemical reactions networks J. Coatl´even and C of oscillations in sufficiently simple reaction networks. Keywords: chemical reaction networks, oscillations, Hopf. Altafini September 10, 2009 Abstract It is known that a kinetic reaction network in which one or more

  14. Supersonic molecular beam experiments on surface chemical reactions.

    PubMed

    Okada, Michio

    2014-10-01

    The interaction of a molecule and a surface is important in various fields, and in particular in complex systems like biomaterials and their related chemistry. However, the detailed understanding of the elementary steps in the surface chemistry, for example, stereodynamics, is still insufficient even for simple model systems. In this Personal Account, I review our recent studies of chemical reactions on single-crystalline Cu and Si surfaces induced by hyperthermal oxygen molecular beams and by oriented molecular beams, respectively. Studies of oxide formation on Cu induced by hyperthermal molecular beams demonstrate a significant role of the translational energy of the incident molecules. The use of hyperthermal molecular beams enables us to open up new chemical reaction paths specific for the hyperthermal energy region, and to develop new methods for the fabrication of thin films. On the other hand, oriented molecular beams also demonstrate the possibility of understanding surface chemical reactions in detail by varying the orientation of the incident molecules. The steric effects found on Si surfaces hint at new ways of material fabrication on Si surfaces. Controlling the initial conditions of incoming molecules is a powerful tool for finely monitoring the elementary step of the surface chemical reactions and creating new materials on surfaces. PMID:25044656

  15. Chemical Reaction due to Stronger Ramachandran Interaction

    E-print Network

    Andrew Das Arulsamy

    2013-12-26

    The origin of a chemical reaction between two reactant atoms is associated to the activation energy, with the assumption that, high-energy collisions between these atoms, are the ones that overcome the activation energy. Here, we (i) show that a stronger attractive van der Waals (vdW) and electron-ion Coulomb interactions between two polarized atoms are responsible to initiate a chemical reaction, either before or after the collision. We derive this stronger vdW attraction formula exactly using the quasi one-dimensional Drude model within the ionization energy theory and the energy-level spacing renormalization group method. Along the way, we (ii) expose the precise physical mechanism responsible for the existence of a stronger vdW interaction for both long and short distances, and also show how to technically avoid the electron-electron Coulomb repulsion between polarized electrons from these two reactant atoms. Finally, we properly and correctly associate the existence of this stronger attraction to Ramachandran's 'normal limits' (distance shorter than what is allowed by the standard vdW bond) between chemically nonbonded atoms.

  16. Chemical and radiation-chemical radical reactions in lignocellulose materials

    NASA Astrophysics Data System (ADS)

    Kuzina, Svetlana I.; Shilova, Irina A.; Mikhailov, Al'fa I.

    2011-09-01

    Chemical and radiation-chemical radical reactions in lignocellulose materials were explored by 3-cm and 2-mm ESR spectroscopy. Background (intrinsic) singlet signals at g=2.003 from wood pulp and lignin and those arising during reaction of lignocellulose materials with acids and chlorine were attributed to radicals with conjugated C?C bonds. The 2-mm ESR signal with 3D anisotropy of g-factor from o-semiquinone radical ions formed in reaction of lignin with NaOH was recorded for the first time. The singlet signals derived from cellulose ?-irradiated at 77 K and marked out during post-thermal reactions were assigned to radicals with conjugated bonds. In wetted cellulose, a triplet signal with ??H?2.7 mT and imposed quadruplet structure (0.5-0.7 mT) from three ?-protons was detected at 300 K and attributed to ? 4-radicals. The triplet signals derived from ? 2- and ? 3-radicals in pyranose cycles of cellulose exhibited higher values of ??H (3.0-3.2 mT) and lower thermal stability (up to 250 K). In radiolyzed cotton pulp, detected were ESR signals derived from formyl radicals formed upon rupture of the ? 5?? 6 bond in pyranose cycles. Heating up irradiated samples under ? 2 was accompanied by formation of peroxide radicals. Photoinduced recombination of trapped electrons with ? 1-radicals was found to proceed as a chain reaction with a kinetic length of about 25 units. Photolysis ( ??360 nm) of radiolyzed cellulose enhanced the disclosure of pyranose cycles and, as a result, the evolution of CO 2 by a factor of 2-2.5.

  17. Chemical Reaction of Silicon Clusters with nitrogen monoxide Chemical reaction of small silicon cluster ions (Si n

    E-print Network

    Maruyama, Shigeo

    Si NO Chemical Reaction of Silicon Clusters with nitrogen monoxide * ** * ** *, ** ABSTRACT Chemical reaction of small silicon cluster ions (Si n + :20 n 30) with ethylene and nitrogen monoxideN + Si28N + Cluster ion mass (amu) Fig.2 Chemical reaction of Si cluster with NO 8 12 16 20 24

  18. On the geometrical thermodynamics of chemical reactions

    E-print Network

    Manuel Santoro; Albert S. Benight

    2005-07-08

    The formal structure of geometrical thermodynamics is reviewed with particular emphasis on the geometry of equilibria submanifolds. On these submanifolds thermodynamic metrics are defined as the Hessian of thermodynamic potentials. Links between geometry and thermodynamics are explored for single and multiple component, closed and open systems. For multi-component closed and open systems the Gibbs free energy is employed as the thermodynamic potential to investigate the connection between geometry and thermodynamics. The Gibbs free energy is chosen for the analysis of multicomponent systems and, in particular, chemical reactions.

  19. Stochastic Chemical Reactions in Micro-domains

    E-print Network

    D. Holcman; Z. Schuss

    2004-12-25

    Traditional chemical kinetics may be inappropriate to describe chemical reactions in micro-domains involving only a small number of substrate and reactant molecules. Starting with the stochastic dynamics of the molecules, we derive a master-diffusion equation for the joint probability density of a mobile reactant and the number of bound substrate in a confined domain. We use the equation to calculate the fluctuations in the number of bound substrate molecules as a function of initial reactant distribution. A second model is presented based on a Markov description of the binding and unbinding and on the mean first passage time of a molecule to a small portion of the boundary. These models can be used for the description of noise due to gating of ionic channels by random binding and unbinding of ligands in biological sensor cells, such as olfactory cilia, photo-receptors, hair cells in the cochlea.

  20. THE JOURNAL OF CHEMICAL PHYSICS 138, 144502 (2013) Speeding chemical reactions by focusing

    E-print Network

    Lindenberg, Katja

    2013-01-01

    THE JOURNAL OF CHEMICAL PHYSICS 138, 144502 (2013) Speeding chemical reactions by focusing A. M for a chemical reaction of colloidal particles which are transported by a laminar fluid and are focused their chemical reaction. Our main result is that reactants that arise from non- homogeneous distributions can

  1. Chemical Master versus Chemical Langevin for First-Order Reaction Networks

    E-print Network

    Mottram, Nigel

    Chemical Master versus Chemical Langevin for First-Order Reaction Networks Desmond J. Higham Raya;1 Motivation A system of chemical reactions at thermal equilibrium is traditionally modelled as a collection in typical chemical reactions, the RRE is a per- fectly adequate model. However, there are some application

  2. Detailed Chemical Kinetic Reaction Mechanism for Biodiesel Components Methyl Stearate and Methyl Oleate

    SciTech Connect

    Naik, C; Westbrook, C K; Herbinet, O; Pitz, W J; Mehl, M

    2010-01-22

    New chemical kinetic reaction mechanisms are developed for two of the five major components of biodiesel fuel, methyl stearate and methyl oleate. The mechanisms are produced using existing reaction classes and rules for reaction rates, with additional reaction classes to describe other reactions unique to methyl ester species. Mechanism capabilities were examined by computing fuel/air autoignition delay times and comparing the results with more conventional hydrocarbon fuels for which experimental results are available. Additional comparisons were carried out with measured results taken from jet-stirred reactor experiments for rapeseed methyl ester fuels. In both sets of computational tests, methyl oleate was found to be slightly less reactive than methyl stearate, and an explanation of this observation is made showing that the double bond in methyl oleate inhibits certain low temperature chain branching reaction pathways important in methyl stearate. The resulting detailed chemical kinetic reaction mechanism includes more approximately 3500 chemical species and more than 17,000 chemical reactions.

  3. Computed Potential Energy Surfaces for Chemical Reactions

    NASA Technical Reports Server (NTRS)

    Heinemann, K.; Walch, Stephen P.; Levin, Eugene

    1993-01-01

    A manuscript describing the calculations on the (1)CH2 + H2O, H2 + HCOH, and H2 + H2CO product channels in the CH3 + OH reaction, which were described in the last progress report, has been accepted for publication in J. Chem. Phys., and a copy of the manuscript is included in the appendix. The production of (1)CH2 in this reaction is important in hydrocarbon combustion since (1)CH2 is highly reactive and would be expected to insert into N2, possibly leading to a new source for prompt NO(x) (vide infra). During the last six months new calculations have been carried out for the NH2 + NO system, which is important in the thermal de-NO(x) process.

  4. CHEMICALS INCORPORATED IN NEST MATERIAL BY RED IMPORTED FIRE ANTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Red imported fire ants are believed to incorporate ant-derived chemicals in nesting material. However, only a few chemicals have been identified. One hurdle for such investigation is the interference in chemical analysis from soil-borne chemicals. Ants were found to be able to construct their nes...

  5. Organic chemical reactions in supercritical water

    SciTech Connect

    Savage, P.E. [Univ. of Michigan, Ann Arbor, MI (United States). Chemical Engineering Dept.] [Univ. of Michigan, Ann Arbor, MI (United States). Chemical Engineering Dept.

    1999-02-01

    Water near or above its critical point (374 C, 218 atm) is attracting increased attention as a medium for organic chemistry. Most of this new attention is driven by the search for more green or environmentally benign chemical processes. Using near-critical or supercritical water (SCW) instead of organic solvents in chemical processes offers environmental advantages and may lead to pollution prevention. Interest in doing chemistry in SCW is not entirely new, however. There has been much previous research in this area with applications in synthetic fuels production, biomass processing, waste treatment, materials synthesis, and geochemistry. Water near its critical point possesses properties very different from those of ambient liquid water. The dielectric constant is much lower, and the number and persistence of hydrogen bonds are both diminished. As a result, high-temperature water behaves like many organic solvents in that organic compounds enjoy high solubilities in near-critical water and complete miscibility with SCW. Moreover, gases are also miscible in SCW so employing a SCW reaction environment provides an opportunity to conduct chemistry in a single fluid phase that would otherwise occur in a multiphase system under more conventional conditions. The paper discusses the use of supercritical water in the following reactions: hydrogenation/dehydrogenation; C-C bond formation; rearrangements; hydration/dehydration; elimination; hydrolysis; partial oxidation; H-D exchange; decomposition; and oxidation.

  6. REGULAR ARTICLE Coordinate reduction for exploring chemical reaction paths

    E-print Network

    Schlegel, H. Bernhard

    REGULAR ARTICLE Coordinate reduction for exploring chemical reaction paths Adam B. Birkholz · H of coordinates can reproduce the changes in geometry along the reaction path with chemical accuracy and may help The potential energy surface for the reaction of a typical molecular system composed of N atoms is defined

  7. Uncertain dynamics in nonlinear chemical reactions Jichang Wang,a

    E-print Network

    Showalter, Kenneth

    Uncertain dynamics in nonlinear chemical reactions Jichang Wang,a Hongyan Sun,b Stephen K. Scottc a dissociation reaction of the autocatalytic species, B ! X + Y, followed by a recombination reaction, X + Y ! C evolution of the system. 1. Introduction The study of nonlinear chemical kinetics has flourished in the past

  8. Plasmon-assisted chemical reactions revealed by high-vacuum tip-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Lu, Shuaicheng; Sheng, Shaoxiang; Zhang, Zhenglong; Xu, Hongxing; Zheng, Hairong

    2014-08-01

    Tip-enhanced Raman spectroscopy (TERS) is the technique that combines the nanoscale spatial resolution of a scanning probe microscope and the highly sensitive Raman spectroscopy enhanced by the surface plasmons. It is suitable for chemical analysis at nanometer scale. Recently, TERS exhibited powerful potential in analyzing the chemical reactions at nanoscale. The high sensitivity and spatial resolution of TERS enable us to learn the reaction processes more clearly. More importantly, the chemical reaction in TERS is assisted by surface plasmons, which provides us an optical method to manipulate the chemical reactions at nanoscale. Here using our home-built high-vacuum tip-enhanced Raman spectroscopy (HV-TERS) setup, we successfully observed the plasmon-assisted molecule dimerization and dissociation reactions. In HV-TERS system, under laser illumination, 4-nitrobenzenethiol (4NBT) molecules can be dimerized to p,p'-dimercaptoazobenzene (DMAB), and dissociation reaction occurs for malachite green (MG) molecules. Using our HV-TERS setup, the dynamic processes of the reactions are clearly revealed. The chemical reactions can be manipulated by controlling the plasmon intensity through changing the power of the incident laser, the tunneling current and the bias voltage. We also investigated the role of plasmonic thermal effect in the reactions by measuring both the Stokes and anti- Stokes Raman peaks. Our findings extend the applications of TERS, which can help to study the chemical reactions and understand the dynamic processes at single molecular level, and even design molecules by the plasmon-assisted chemical reactions.

  9. Towards chemically accurate simulation of molecule-surface reactions.

    PubMed

    Kroes, Geert-Jan

    2012-11-21

    This perspective addresses four challenges facing theorists whose aim is to make quantitatively accurate predictions for reactions of molecules on metal surfaces, and suggests ways of meeting these challenges, focusing on dissociative chemisorption reactions of H(2), N(2), and CH(4). Addressing these challenges is ultimately of practical importance to a more accurate description of overall heterogeneously catalysed reactions, which play a role in the production of more than 90% of man-made chemicals. One challenge is to describe the interaction of a molecule with a metal surface with chemical accuracy, i.e., with errors in reaction barrier heights less than 1 kcal mol(-1). In this framework, the potential of a new implementation of specific reaction parameter density functional theory (SRP-DFT) will be discussed, with emphasis on applications to reaction of H(2) with metal surfaces. Two additional challenges are to come up with improved descriptions of the effects of phonons and electron-hole pairs on reaction of molecules like N(2) on metal surfaces. Phonons can be tackled using sudden approximations in quantum dynamics, and through Ab Initio Molecular Dynamics (AIMD) calculations using classical dynamics. To additionally achieve an accurate description of the effect of electron-hole pair excitation on dissociative chemisorption within a classical dynamics framework, it may be possible to combine AIMD with electronic friction. The fourth challenge we will consider is how to achieve an accurate quantum mechanical description of the dissociative chemisorption of a polyatomic molecule, like methane, on a metal surface. A method of potential interest is the Multi-Configuration Time-Dependent Hartree (MCTDH) method. PMID:23037951

  10. Thermodynamic performance for a chemical reactions model

    NASA Astrophysics Data System (ADS)

    Gonzalez-Narvaez, R. E.; Sánchez-Salas, N.; Chimal-Eguía, J. C.

    2015-01-01

    This paper presents the analysis efficiency of a chemical reaction model of four states, such that their activated states can occur at any point (fixed but arbitrary) of the transition from one state to another. This mechanism operates under a single heat reservoir temperature, unlike the internal combustion engines where there are two thermal sources. Different efficiencies are compared to this model, which operate at different optimum engine regimes. Thus, some analytical methods are used to give an approximate expression, facilitating the comparison between them. Finally, the result is compared with that obtained by other authors considered a general model of an isothermal molecular machine. Taking into account the above, the results seems to follow a similar behaviour for all the optimized engines, which resemble that observed in the case of heat engine efficiencies.

  11. Robust Stochastic Chemical Reaction Networks and Bounded Tau-Leaping

    Microsoft Academic Search

    David Soloveichik

    2008-01-01

    The behavior of some stochastic chemical reaction networks is largely unaffected by slight inaccuracies in reaction rates. We formalize the robustness of state probabilities to reaction rate deviations, and describe a formal connection between robustness and efficiency of simulation. Without robustness guarantees, stochastic simulation seems to require computational time proportional to the total number of reaction events. Even if the

  12. Quantum dynamics of chemical reactions by converged algebraic variational calculations

    Microsoft Academic Search

    Donald G. Truhlar; David W. Schwenke; Donald J. Kouri

    1990-01-01

    This paper describes recent progress in using algebraic variational methods and L² basis sets for converged quantum mechanical calculations of chemical reaction dynamics of the H + Hâ, O + Hâ, H + HBr, and F + Hâ reactions and the isotopically substituted reactions D + Hâ and O + HD and some of the reverse reactions. The paper emphasizes

  13. Some chemical and mineralogical considerations important for understanding leachate chemistry

    SciTech Connect

    Peterson, E.J.; Wagner, P.

    1982-01-01

    Both the raw shale material and the retorting process parameters are influential in determining the subsequent behavior of the spent shale solids with respect to leaching and/or environmental weathering. The process parameters define the mineral reactions that occur to form the mineral assemblage in the spent shale, while the major and trace element residences and mobilities from the raw shale determine the extent of incorporation of these elements in the spent shale matrix and ultimately the composition of leachate generated by the spent shale solid: water interaction. In order to understand leachate compositions, it is necessary to determine this water: solid interaction, but the solid wastes being considered are a dependent function of the raw shale material and the process parameters. Thus, in order to understand the chemical principles operative in leachate generation, it is necessary to elucidate the interplay of the raw material and the process parameters in the formation of the waste and then the interaction of the waste form with water. The leachate and the solid waste are dependent variables, while the raw shale and the process parameters are independent variables. These considerations are illustrated by results of chemical characterization and experimental studies of field generated spent shales. Results from field generated materials are used to describe important considerations relative to the understanding of leachate chemistry.

  14. GREEN CHEMICAL SYNTHESIS THROUGH CATALYSIS AND ALTERNATE REACTION CONDITIONS

    EPA Science Inventory

    Green chemical synthesis through catalysis and alternate reaction conditions Encompassing green chemistry techniques and methodologies, we have initiated several projects at the National Risk Management Research laboratory that focus on the design and development of chemic...

  15. Prediction and Prevention of Chemical Reaction Hazards: Learning by Simulation.

    ERIC Educational Resources Information Center

    Shacham, Mordechai; Brauner, Neima; Cutlip, Michael B.

    2001-01-01

    Points out that chemical hazards are the major cause of accidents in chemical industry and describes a safety teaching approach using a simulation. Explains a problem statement on exothermic liquid-phase reactions. (YDS)

  16. THE JOURNAL OF CHEMICAL PHYSICS 139, 165104 (2013) Exploring chemical reaction mechanisms through harmonic Fourier beads

    E-print Network

    2013-01-01

    THE JOURNAL OF CHEMICAL PHYSICS 139, 165104 (2013) Exploring chemical reaction mechanisms through understanding of complex chemical transformations relies on the identification of elementary reactions involved the harmonic Fourier beads (HFB) path optimization method to study chemical re- actions involving covalent bond

  17. Direct Monte Carlo simulation of chemical reaction systems: Simple bimolecular reactions

    E-print Network

    Anderson, James B.

    Direct Monte Carlo simulation of chemical reaction systems: Simple bimolecular reactions Shannon D and understanding the behavior of gas phase chemical reaction systems. This Monte Carlo method, originated by Bird useful, and the gas dynamics of many systems is more easily predicted and understood by using Monte Carlo

  18. CHEMSIMUL --a tool for simulating chemical reaction systems Peter Kirkegaard, Erling Bjergbakke, and Frank Markert

    E-print Network

    CHEMSIMUL -- a tool for simulating chemical reaction systems Peter Kirkegaard, Erling Bjergbakke difficult to study elementary chemical reactions without interference from simul- taneous side reactions simulator of chemical kinetics with the following main compo- nents: - Module for input of reaction

  19. Thermophoretic transport in impinging flows including chemical reactions

    NASA Astrophysics Data System (ADS)

    Hsu, Frank Kuan-Chao

    The research constitutes a fundamental study of transport phenomena that has applications to the fabrication of optical fibers. The flow, heat and mass transfer with chemical reactions, and thermophoretic transport of silica particles are studied. The governing equations have been formulated and solved to determine the velocity, temperature and species concentrations, and the effects of buoyancy, variable properties, chemical reactions, and thermophoretic transport on deposition uniformity and efficiency. A path-line/stream-line approach for determining variable particle concentration stagnation deposition with thermophoretic transport is introduced. The research is of fundamental interest and has applications to optical fiber fabrication. A review of the thermophoresis phenomena is provided including a recommended treatment for the thermophoretic coefficient, K. A discussion of the related chemical reactions is given. A study of a H2-N 2 non-premixed jet flame is performed to appraise the proposed H2 oxidation reaction rate and heat release rate. The present results of the velocity and temperature distributions are in very good agreement with the published experimental data. A study of silica (SiO2) particle transport in a free jet system is carried out. The gas entrainment and the thermophoretic transport are two important parameters that determine the particle transport. Both non-reacting and reacting jet flows are studied. The effects of inclination of jet flows on particle transport are also studied. A path-line/stream-line approach for determining deposition with thermophoretic transport in stagnation flow is introduced. This approach allows a variable particle concentration inlet boundary condition to be used. A closed form solution is achieved using this approach. Numerical studies of deposition on a cylindrical preform for both non-reacting and reacting jets are also investigated. A study of a small scale fiber fabrication is made with a cylindrical preform and two burners. Of special interest are the effects of preform temperature and preform thermal conductivity on the deposition efficiency.

  20. Slow chemical reactions in power plant plumes: application to sulfates

    SciTech Connect

    Forney, L.J.; Giz, Z.G.

    1980-01-01

    Slow chemical reactions in which plume travel time is short compared with characteristic chemical reaction times are incorporated into the MIT buoyant plume theory. Conservation equations are written for a buoyant plume in a crosswind. Approximate solutions to the conservation equations are derived and compared with numerical results. Approximate solutions compared favorably with representative field data. (1 diagram, 4 graphs, 29 references, 1 table)

  1. On the rate of relativistic surface chemical reactions.

    PubMed

    Veitsman, E V

    2004-07-15

    On the basis of special relativity and the classical theory of chemical reaction rates it is shown how the surface chemical reaction rates vary as v --> c, where v is the velocity of the object under study and c is the velocity of light. PMID:15178286

  2. Mesoscale simulations of shockwave energy dissipation via chemical reactions.

    PubMed

    Antillon, Edwin; Strachan, Alejandro

    2015-02-28

    We use a particle-based mesoscale model that incorporates chemical reactions at a coarse-grained level to study the response of materials that undergo volume-reducing chemical reactions under shockwave-loading conditions. We find that such chemical reactions can attenuate the shockwave and characterize how the parameters of the chemical model affect this behavior. The simulations show that the magnitude of the volume collapse and velocity at which the chemistry propagates are critical to weaken the shock, whereas the energetics in the reactions play only a minor role. Shock loading results in transient states where the material is away from local equilibrium and, interestingly, chemical reactions can nucleate under such non-equilibrium states. Thus, the timescales for equilibration between the various degrees of freedom in the material affect the shock-induced chemistry and its ability to attenuate the propagating shock. PMID:25725713

  3. Mesoscale simulations of shockwave energy dissipation via chemical reactions

    NASA Astrophysics Data System (ADS)

    Antillon, Edwin; Strachan, Alejandro

    2015-02-01

    We use a particle-based mesoscale model that incorporates chemical reactions at a coarse-grained level to study the response of materials that undergo volume-reducing chemical reactions under shockwave-loading conditions. We find that such chemical reactions can attenuate the shockwave and characterize how the parameters of the chemical model affect this behavior. The simulations show that the magnitude of the volume collapse and velocity at which the chemistry propagates are critical to weaken the shock, whereas the energetics in the reactions play only a minor role. Shock loading results in transient states where the material is away from local equilibrium and, interestingly, chemical reactions can nucleate under such non-equilibrium states. Thus, the timescales for equilibration between the various degrees of freedom in the material affect the shock-induced chemistry and its ability to attenuate the propagating shock.

  4. Microwave-assisted synthesis of chromenes: biological and chemical importance.

    PubMed

    Patil, Shivaputra A; Patil, Siddappa A; Patil, Renukadevi

    2015-06-01

    Chromenes constitute chemically important class of heterocyclic compounds having diverse biological and chemical importance. Development of environmentally benign, efficient and economical methods for the synthesis of chromenes remains a significant challenge in synthetic chemistry. The synthesis of chromenes, therefore, has attracted enormous attention from medicinal and organic chemists. Researchers have embraced the concepts of microwave (high speed) synthesis to produce biologically and chemically important chromenes in a time sensitive manner. This review will summarize the recent biological applications such as anticancer, antimicrobial, neurodegenerative and insecticidal activity of new chromenes prepared via microwave irradiation. The development of new methodologies for the synthesis of chromenes including green chemistry processes has also been discussed. PMID:26061107

  5. Mechano-chemical coupling in Belousov-Zhabotinskii reactions.

    PubMed

    Klika, Václav; Grmela, Miroslav

    2014-03-28

    Mechano-chemical coupling has been recently recognised as an important effect in various systems as chemical reactivity can be controlled through an applied mechanical loading. Namely, Belousov-Zhabotinskii reactions in polymer gels exhibit self-sustained oscillations and have been identified to be reasonably controllable and definable to the extent that they can be harnessed to perform mechanical work at specific locations. In this paper, we use our theoretical work of nonlinear mechano-chemical coupling and investigate the possibility of providing an explanation of phenomena found in experimental research by means of this theory. We show that mechanotransduction occurs as a response to both static and dynamic mechanical stimulation, e.g., volume change and its rate, as observed experimentally and discuss the difference of their effects on oscillations. Plausible values of the quasi-stoichiometric parameter f of Oregonator model are estimated together with its dependence on mechanical stimulation. An increase in static loading, e.g., pressure, is predicted to have stimulatory effect whereas dynamic loading, e.g., rate of volume change, is predicted to be stimulatory only up to a certain threshold. Further, we offer a physically consistent explanation of the observed phenomena why some Belousov-Zhabotinskii gels require an additional mechanical stimulation to show emergence of oscillation or why "revival" of oscillations in Belousov-Zhabotinskii reactions is possible together with indications for further experimental setups. PMID:24697427

  6. LIGAND: database of chemical compounds and reactions in biological pathways

    Microsoft Academic Search

    Susumu Goto; Yasushi Okuno; Masahiro Hattori; Takaaki Nishioka; Minoru Kanehisa

    2002-01-01

    LIGAND is a composite database comprising three sections: COMPOUND for the information about metabolites and other chemical compounds, REACTION for the collection of substrate-product relations representing metabolic and other reactions, and ENZYME for the information about enzyme molecules. The current release (as of September 7, 2001) includes 7298 compounds, 5166 reactions and 3829 enzymes. In addition to the keyword search

  7. Exact Stochastic Simulation of Chemical Reactions with Cycle Leaping*

    E-print Network

    Bruck, Jehoshua (Shuki)

    Exact Stochastic Simulation of Chemical Reactions with Cycle Leaping* Marc D. Riedel Jehoshua Bruck. It tracks in- teger quantities of the molecular species, executing reactions at random based on propensity the re- sults of repeated trials. Unfortunately, for models with many reaction channels and many species

  8. Advanced Chemical Heat Pumps Using Liquid-Vapor Reactions

    E-print Network

    Kirol, L.

    ADVANCED CHEMICAL HEAT PUMPS USING LIQUID-VAPOR REACTIONS LANCE KIROL Senior Program Specialist Idaho National Engineering Laboratory Idaho Falls, Idaho . ABSTRACT Chemical heat pumps utilizing liquid-vapor reactions can be configured... characteristics. A waste heat driven heat pump (temperature amplifier) using liquid-vapor chem1cal reactions- can oper ate with higher coefficient of performance and smaller heat exchangers than an absorption temp erature amplifying heat pump. Higher tempera...

  9. Formal modeling of a system of chemical reactions under uncertainty.

    PubMed

    Ghosh, Krishnendu; Schlipf, John

    2014-10-01

    We describe a novel formalism representing a system of chemical reactions, with imprecise rates of reactions and concentrations of chemicals, and describe a model reduction method, pruning, based on the chemical properties. We present two algorithms, midpoint approximation and interval approximation, for construction of efficient model abstractions with uncertainty in data. We evaluate computational feasibility by posing queries in computation tree logic (CTL) on a prototype of extracellular-signal-regulated kinase (ERK) pathway. PMID:25362839

  10. Chemical Kinetics: As Important As The Second Law Of Thermodynamics?

    Microsoft Academic Search

    FRANK L. LAMBERT

    1998-01-01

    The second law may be ‘time’s arrow’ but activation energies (chemical kinetics) prevent second law predictions from occurring for femtoseconds to eons. This is humanly important: Activation energies not only protect all the organic chemicals in our bodies and our oxidizable possessions from instant combustion in air, but also our breakable skis and surfboards (and legs) from disastrous fracture. Murphy’s

  11. Incidents of chemical reactions in cell equipment

    SciTech Connect

    Baldwin, N.M.; Barlow, C.R. [Uranium Enrichment Organization, Oak Ridge, TN (United States)

    1991-12-31

    Strongly exothermic reactions can occur between equipment structural components and process gases under certain accident conditions in the diffusion enrichment cascades. This paper describes the conditions required for initiation of these reactions, and describes the range of such reactions experienced over nearly 50 years of equipment operation in the US uranium enrichment program. Factors are cited which can promote or limit the destructive extent of these reactions, and process operations are described which are designed to control the reactions to minimize equipment damage, downtime, and the possibility of material releases.

  12. Deterministic Function Computation with Chemical Reaction Networks.

    PubMed

    Chen, Ho-Lin; Doty, David; Soloveichik, David

    2012-01-01

    Chemical reaction networks (CRNs) formally model chemistry in a well-mixed solution. CRNs are widely used to describe information processing occurring in natural cellular regulatory networks, and with upcoming advances in synthetic biology, CRNs are a promising language for the design of artificial molecular control circuitry. Nonetheless, despite the widespread use of CRNs in the natural sciences, the range of computational behaviors exhibited by CRNs is not well understood. CRNs have been shown to be efficiently Turing-universal (i.e., able to simulate arbitrary algorithms) when allowing for a small probability of error. CRNs that are guaranteed to converge on a correct answer, on the other hand, have been shown to decide only the semilinear predicates (a multi-dimensional generalization of "eventually periodic" sets). We introduce the notion of function, rather than predicate, computation by representing the output of a function f : ? (k) ? ? (l) by a count of some molecular species, i.e., if the CRN starts with x 1, …, xk molecules of some "input" species X 1, …, Xk , the CRN is guaranteed to converge to having f(x 1, …, xk ) molecules of the "output" species Y 1, …, Yl . We show that a function f : ? (k) ? ? (l) is deterministically computed by a CRN if and only if its graph {(x, y) ? ? (k) × ? (l) ? f(x) = y} is a semilinear set. Finally, we show that each semilinear function f (a function whose graph is a semilinear set) can be computed by a CRN on input x in expected time O(polylog ?x?1). PMID:25383068

  13. Synthesis and Decomposition of Zinc Iodide: Model Reactions for Investigating Chemical Change in the Introductory Laboratory

    Microsoft Academic Search

    Stephen Demeo

    1995-01-01

    The purpose of this article is to discuss two colorful reactions not widely used by chemical educators in high schools or college chemistry laboratories: The synthesis of zinc iodide from its elements, zinc and iodine, and the subsequent decomposition of zinc iodide back into its elements. These reactions are important for chemistry teachers to know about because they can be

  14. Flow Tube Studies of Gas Phase Chemical Processes of Atmospheric Importance

    NASA Technical Reports Server (NTRS)

    Molina, Mario J.

    1997-01-01

    The objective of this project is to conduct measurements of elementary reaction rate constants and photochemistry parameters for processes of importance in the atmosphere. These measurements are being carried out under temperature and pressure conditions covering those applicable to the stratosphere and upper troposphere, using the chemical ionization mass spectrometry turbulent flow technique developed in our laboratory.

  15. Injectivity of chemical reaction networks with mass action kinetics revisited

    E-print Network

    Feliu, Elisenda

    2011-01-01

    In this work we extend the characterization of injectivity via the Jacobian criterion first developed by Craciun and Feinberg for chemical reaction networks with outflow reactions to arbitrary chemical reaction networks taken with mass action kinetics. Injective chemical reaction networks do not have the capacity to admit multiple positive steady states for any rate constants and within each stoichiometric class. It is shown that a network is injective if and only if the determinant of the Jacobian of the system of ordinary differential equations associated to the network never vanishes. The determinant is a polynomial on the species concentrations and the rate constants, and its coefficients are fully determined. Previous works apply to chemical reaction networks whose stoichiometric space has maximal dimension. Here we present a direct route, independent of the dimension of the stoichiometric space which precludes at the same time the existence of degenerate steady states.

  16. CHEMICAL TAILORING OF TEICOPLANIN WITH SITE-SELECTIVE REACTIONS

    PubMed Central

    Pathak, Tejas P.; Miller, Scott J.

    2013-01-01

    Semi-synthesis of natural product derivatives combines the power of fermentation with orthogonal chemical reactions. Yet, chemical modification of complex structures represents an unmet challenge, as poor selectivity often undermines efficiency. The complex antibiotic teicoplanin eradicates bacterial infections. However, as resistance emerges, the demand for improved analogs grows. We have discovered chemical reactions that achieve site-selective alteration of teicoplanin. Utilizing peptide-based additives that alter reaction selectivities, certain bromo-teicoplanins are accessible. These new compounds are also scaffolds for selective cross-coupling reactions, enabling further molecular diversification. These studies enable two-step access to glycopeptide analogs not available through either biosynthesis or rapid total chemical synthesis alone. The new compounds exhibit a spectrum of activities, revealing that selective chemical alteration of teicoplanin may lead to analogs with attenuated or enhanced antibacterial properties, in particular against vancomycin and teicoplanin resistance strains. PMID:23692563

  17. Chemical Demonstrations with Consumer Chemicals: The Black and White Reaction.

    ERIC Educational Resources Information Center

    Wright, Stephen W.

    2002-01-01

    Describes a dramatic chemical demonstration in which chemicals that are black and white combine to produce a colorless liquid. Reactants include tincture of iodine, bleach, white vinegar, Epsom salt, vitamin C tablets, and liquid laundry starch. (DDR)

  18. Chemical Looping Combustion Reactions and Systems

    SciTech Connect

    Sarofim, Adel; Lighty, JoAnn; Smith, Philip; Whitty, Kevin; Eyring, Edward; Sahir, Asad; Alvarez, Milo; Hradisky, Michael; Clayton, Chris; Konya, Gabor; Baracki, Richard; Kelly, Kerry

    2011-07-01

    Chemical Looping Combustion (CLC) is one promising fuel-combustion technology, which can facilitate economic CO2 capture in coal-fired power plants. It employs the oxidation/reduction characteristics of a metal, or oxygen carrier, and its oxide, the oxidizing gas (typically air) and the fuel source may be kept separate. This work focused on two classes of oxygen carrier, one that merely undergoes a change in oxidation state, such as Fe3O4/Fe2O3 and one that is converted from its higher to its lower oxidation state by the release of oxygen on heating, i.e., CuO/Cu2O. This topical report discusses the results of four complementary efforts: (1) the development of process and economic models to optimize important design considerations, such as oxygen carrier circulation rate, temperature, residence time; (2) the development of high-performance simulation capabilities for fluidized beds and the collection, parameter identification, and preliminary verification/uncertainty quantification (3) the exploration of operating characteristics in the laboratory-scale bubbling bed reactor, with a focus on the oxygen carrier performance, including reactivity, oxygen carrying capacity, attrition resistance, resistance to deactivation, cost and availability (4) the identification of mechanisms and rates for the copper, cuprous oxide, and cupric oxide system using thermogravimetric analysis.

  19. Non-equilibrium effects in high temperature chemical reactions

    NASA Technical Reports Server (NTRS)

    Johnson, Richard E.

    1987-01-01

    Reaction rate data were collected for chemical reactions occurring at high temperatures during reentry of space vehicles. The principle of detailed balancing is used in modeling kinetics of chemical reactions at high temperatures. Although this principle does not hold for certain transient or incubation times in the initial phase of the reaction, it does seem to be valid for the rates of internal energy transitions that occur within molecules and atoms. That is, for every rate of transition within the internal energy states of atoms or molecules, there is an inverse rate that is related through an equilibrium expression involving the energy difference of the transition.

  20. Morphological changes of amphiphilic molecular assemblies induced by chemical reactions.

    PubMed

    Nakagawa, Koh M; Noguchi, Hiroshi

    2015-02-01

    Shape transformations of amphiphilic molecular assemblies induced by chemical reactions are studied using coarse-grained molecular simulations. A binding reaction between hydrophilic and hydrophobic molecules is considered. It is found that the reaction induces transformation of an oil droplet to a tubular vesicle via bicelles and vesicles with discoidal arms. The discoidal arms close into vesicles, which are subsequently fused into the tubular vesicle. Under the chemical reaction, the bicelle-to-vesicle transition occurs at smaller sizes than in the absence of the hydrophobic molecules. It is revealed that the enhancement of this transition is due to embedded hydrophobic particles that reduce the membrane bending rigidity. PMID:25582908

  1. Morphological changes of amphiphilic molecular assemblies induced by chemical reactions

    NASA Astrophysics Data System (ADS)

    Nakagawa, Koh M.; Noguchi, Hiroshi

    Shape transformations of amphiphilic molecular assemblies induced by chemical reaction are studied using coarse-grained molecular simulations. A binding reaction between hydrophilic and hydrophobic molecules is considered. It is found that the reaction induces transformation of an oil droplet to a tubular vesicle via bicelles and vesicles with discoidal arms. The discoidal arms close into vesicles, which are subsequently fused into the tubular vesicle. Under the chemical reaction, the bicelle-to-vesicle transition occurs at smaller sizes than in the absence of the hydrophobic molecules. It is revealed that the enhancement of this transition is due to embedded hydrophobic particles that reduce the membrane bending rigidity.

  2. Morphological changes of amphiphilic molecular assemblies induced by chemical reaction

    E-print Network

    Koh M. Nakagawa; Hiroshi Noguchi

    2014-11-21

    Shape transformations of amphiphilic molecular assemblies induced by chemical reaction are studied using coarse-grained molecular simulations. A binding reaction between hydrophilic and hydrophobic molecules is considered. It is found that the reaction induces transformation of an oil droplet to a tubular vesicle via bicelles and vesicles with discoidal arms. The discoidal arms close into vesicles, which are subsequently fused into the tubular vesicle. Under the chemical reaction, the bicelle-to-vesicle transition occurs at smaller sizes than in the absence of the hydrophobic molecules. It is revealed that the enhancement of this transition is due to embedded hydrophobic particles that reduce the membrane bending rigidity.

  3. Developing Secondary Students' Conceptions of Chemical Reactions: The Introduction of Chemical Equilibrium.

    ERIC Educational Resources Information Center

    Van Driel, Jan H.; De Vos, Wobbe; Verloop, Nico; Dekkers, Hetty

    1998-01-01

    Describes an empirical study concerning the introduction of the concept of chemical equilibrium in chemistry classrooms in a way which challenges students' initial conceptions of chemical reactions. Contains 23 references. (DDR)

  4. The Activated Complex in Chemical Reactions

    Microsoft Academic Search

    Henry Eyring

    1935-01-01

    The calculation of absolute reaction rates is formulated in terms of quantities which are available from the potential surfaces which can be constructed at the present time. The probability of the activated state is calculated using ordinary statistical mechanics. This probability multiplied by the rate of decomposition gives the specific rate of reaction. The occurrence of quantized vibrations in the

  5. The Fluid Mechanics of Chemical Reaction

    NASA Astrophysics Data System (ADS)

    Benson, D. A.; Engdahl, N. B.; Bolster, D.

    2014-12-01

    The ability for reactive constituents to mix is often the key limiting factor for the completion of reactions across a huge range of scales in a variety of media. In flowing systems, deformation and shear enhance mixing by bringing constituents into closer proximity, thus increasing reaction potential. Accurately quantifying this enhanced mixing is key to predicting reactions, and typically is done by observing or simulating scalar transport. To eliminate this computationally expensive step, we use a Lagrangian stochastic framework to derive the enhancement to reaction potential by calculating the collocation probability of particle pairs in a heterogeneous flow field accounting for deformations. We relate the enhanced reaction potential to three well-known flow topology metrics (Okubo-Weiss, finite-time Lyapunov exponent, and right Cauchy-Green tensor) and demonstrate that it is best correlated to the largest eigenvalue of the right Cauchy-Green tensor. The reason is that this eigenvalue reflects compression and shear but ignores rotation, which does not enhance mixing. We demonstrate that regions of high shear and/or compression do indeed have higher rates of reaction in particle-tracking reaction simulations, but this is not necessarily seen in traditional Eulerian simulations due to numerical (artificial) mixing and the amplification of these errors by non-linear reactions.

  6. Charge Exchange and Chemical Reactions with Trapped Th$^{3+}$

    E-print Network

    Churchill, L R; Chapman, M S

    2010-01-01

    We have measured the reaction rates of trapped, buffer gas cooled Th$^{3+}$ and various gases and have analyzed the reaction products using trapped ion mass spectrometry techniques. Ion trap lifetimes are usually limited by reactions with background molecules, and the high electron affinity of multiply charged ions such as Th$^{3+}$ make them more prone to loss. Our results show that reactions of Th$^{3+}$ with carbon dioxide, methane, and oxygen all occur near the classical Langevin rate, while reaction rates with argon, hydrogen, and nitrogen are orders of magnitude lower. Reactions of Th$^{3+}$ with oxygen and methane proceed primarily via charge exchange, while simultaneous charge exchange and chemical reaction occurs between Th$^{3+}$ and carbon dioxide. Loss rates of Th$^{3+}$ in helium are consistent with reaction with impurities in the gas. Reaction rates of Th$^{3+}$ with nitrogen and argon depend on the internal electronic configuration of the Th$^{3+}$.

  7. The How and Why of Chemical Reactions

    ERIC Educational Resources Information Center

    Schubert, Leo

    1970-01-01

    Presents a discussion of some of the fundamental concepts in thermodynamics and quantum mechanics including entropy, enthalpy, free energy, the partition function, chemical kinetics, transition state theory, the making and breaking of chemical bonds, electronegativity, ion sizes, intermolecular energies and of their role in explaining the nature…

  8. Organic chemical reactions in supercritical water

    Microsoft Academic Search

    Phillip E. Savage

    1999-01-01

    Water near or above its critical point (374 C, 218 atm) is attracting increased attention as a medium for organic chemistry. Most of this new attention is driven by the search for more green or environmentally benign chemical processes. Using near-critical or supercritical water (SCW) instead of organic solvents in chemical processes offers environmental advantages and may lead to pollution

  9. Application of Reversible Chemical Reactions for Temperature Amplification 

    E-print Network

    Ally, M. R.; Rebello, W. J.; Suciu, D. F.

    1985-01-01

    temperature thermal energy, mechanical and absorption type heat pumps have been proposed and developed so far. This paper addresses itself to the concept of a heat reaction chemical heat pump (HRCHP). The HRCHP concept is aimed to upgrade low temperature...

  10. Advanced Chemical Heat Pumps Using Liquid-Vapor Reactions 

    E-print Network

    Kirol, L.

    1987-01-01

    Chemical heat pumps utilizing liquid-vapor reactions can be configured in forms analogous to electric drive vapor-compression heat pumps and heat activated absorption heat pumps. Basic thermodynamic considerations eliminate some heat pumps and place...

  11. Log-domain circuit models of chemical reactions

    E-print Network

    Mandal, Soumyajit

    We exploit the detailed similarities between electronics and chemistry to develop efficient, scalable bipolar or subthreshold log-domain circuits that are dynamically equivalent to networks of chemical reactions. Our ...

  12. 29. NORTHWEST VIEW OF BOILER FEEDWATER CHEMICAL REACTION TANKS, WITH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    29. NORTHWEST VIEW OF BOILER FEEDWATER CHEMICAL REACTION TANKS, WITH FORMER GENERAL OFFICE BUILDING IN BACKGROUND. - U.S. Steel Duquesne Works, Fuel & Utilities Plant, Along Monongahela River, Duquesne, Allegheny County, PA

  13. Application of Reversible Chemical Reactions for Temperature Amplification

    E-print Network

    Ally, M. R.; Rebello, W. J.; Suciu, D. F.

    temperature thermal energy, mechanical and absorption type heat pumps have been proposed and developed so far. This paper addresses itself to the concept of a heat reaction chemical heat pump (HRCHP). The HRCHP concept is aimed to upgrade low temperature...

  14. Determining Interconnections in Chemical Reaction Networks Antonis Papachristodoulou and Ben Recht

    E-print Network

    Nowak, Robert

    Determining Interconnections in Chemical Reaction Networks Antonis Papachristodoulou and Ben Recht Abstract-- We present a methodology for robust determina- tion of chemical reaction network' dynamics. We illustrate our methodology on a hypothetical chemical reaction network under various

  15. APRIORI BOUNDS FOR REACTION-DIFFUSION SYSTEMS ARISING IN CHEMICAL JEFF S. MCGOUGH AND KYLE RILEY

    E-print Network

    McGough, Jeff S.

    APRIORI BOUNDS FOR REACTION-DIFFUSION SYSTEMS ARISING IN CHEMICAL KINETICS JEFF S. MCGOUGH AND KYLE RILEY Abstract. The authors investigate reaction diffusion equations which arise in chemical kinetics diffusion equations, gradient bounds, chemical kinetics, autocatalytic reactions AMS subject classifications

  16. CHEMICAL REACTIONS SIMULATED BY GROUND-WATER-QUALITY MODELS.

    USGS Publications Warehouse

    Grove, David B.; Stollenwerk, Kenneth G.

    1987-01-01

    Recent literature concerning the modeling of chemical reactions during transport in ground water is examined with emphasis on sorption reactions. The theory of transport and reactions in porous media has been well documented. Numerous equations have been developed from this theory, to provide both continuous and sequential or multistep models, with the water phase considered for both mobile and immobile phases. Chemical reactions can be either equilibrium or non-equilibrium, and can be quantified in linear or non-linear mathematical forms. Non-equilibrium reactions can be separated into kinetic and diffusional rate-limiting mechanisms. Solutions to the equations are available by either analytical expressions or numerical techniques. Saturated and unsaturated batch, column, and field studies are discussed with one-dimensional, laboratory-column experiments predominating. A summary table is presented that references the various kinds of models studied and their applications in predicting chemical concentrations in ground waters.

  17. Kinetics of Heterogeneous Chemical Reactions, II*

    PubMed Central

    Lin, S. H.; Eyring, H.

    1970-01-01

    The first-order and zero-order kinetics of heterogeneous reactions coupled with the diffusion process are studied. The differential equations of these reaction systems are solved for the cases in which the fluid is not stirred and the fluid is well stirred. It is shown that both the rate constants and the diffusion coefficient can be determined in various ways depending on the experimental conditions. PMID:5263761

  18. Development of the reaction time accelerating molecular dynamics method for simulation of chemical reaction

    NASA Astrophysics Data System (ADS)

    Takaba, Hiromitsu; Hayashi, Shigekazu; Zhong, Huifeng; Malani, Hema; Suzuki, Ai; Sahnoun, Riadh; Koyama, Michihisa; Tsuboi, Hideyuki; Hatakeyama, Nozomu; Endou, Akira; Kubo, Momoji; Del Carrpio, Carlos A.; Miyamoto, Akira

    2008-09-01

    We present a novel and efficient method to integrate chemical reactions into molecular dynamics to simulate chemical reaction systems. We have dubbed this method RTAMD, an acronym for reaction time accelerating molecular dynamics. The methodology we propose here requires no more than the knowledge of the empirical intermolecular potentials for the species at play as well as the elementary reaction path among them. Bond formation during the simulation is performed by changing the inter-atomic potentials from those of the non-bonded species to those of the bonded ones, and a reaction is deemed to occur by the distance separating the bond forming atoms. In this way the energy barrier for a reaction is no longer considered; the estimation of the reaction rate, however, is possible by introducing the principles of the transition state theory. The simplicity of the present scheme to simulate chemical reactions enables it to be used in large-scale MD simulations involving a large number of simultaneous chemical reactions and to evaluate kinetic parameters. In this paper, the basic theory of the method is presented and application to simple equiatomic reaction system where the reaction rates were estimated was illustrated.

  19. Shock-induced chemical reactions and synthesis of nickel aluminides

    Microsoft Academic Search

    I. Song; N. N. Thadhani

    1992-01-01

    Chemical reactions in Ni and Al powder mixtures, initiated by the passage of shock waves, are used for the synthesis of nickel\\u000a aluminides. Mechanistic investigations reveal that the extent of these shock-induced chemical reactions and the type (stoichiometry)\\u000a of shock-synthesized compound formed depend on shock-loading conditions and the initial powder particle morphology. More intense\\u000a shock conditions and irregular powder morphology

  20. Chemical pathways in ultracold reactions of SrF molecules

    E-print Network

    Meyer, Edmund R

    2011-01-01

    We present a theoretical investigation of the chemical reaction SrF + SrF $\\rightarrow$ products, focusing on reactions at ultralow temperatures. We find that bond swapping, SrF + SrF $\\rightarrow$ Sr$_2$ + F$_2$, is energetically forbidden at these temperatures. Rather, the only energetically allowed reaction is SrF + SrF $\\rightarrow$ SrF$_2$ + Sr, and even then only singlet states of the SrF$_2$ trimer can form. A calculation along a reduced reaction path demonstrates that this abstraction reaction is barrierless, and proceeds by one SrF molecule "handing off" a fluorine atom to the other molecule.

  1. Ozone - plant surface reactions an important ozone loss term?

    NASA Astrophysics Data System (ADS)

    Hansel, Armin; Jud, Werner; Fischer, Lukas; Canaval, Eva; Wohlfahrt, Georg; Tissier, Alain

    2015-04-01

    Elevated tropospheric ozone concentrations are considered a toxic threat to plants responsible for global crop losses with associated economic costs of several billions dollar per year. Plant injuries have been related to the uptake of ozone through stomatal pores and oxidative effects damaging the internal leaf tissue. But a striking question remains: How much ozone enters the plant through open stomata and how much ozone is lost by chemical reactions at the plant surface? Until now surface losses are estimated from measured total ozone deposition fluxes and calculated stomatal conductance values. While stomatal conductance of CO2 and H2O is well understood and extensively used in describing plant atmosphere gas exchange, stomatal conductance of ozone is not well known. Here we use different Nicotiana tabacum varieties and find that surface reactions of ozone with diterpenoids synthesized by glandular trichomes reduce ozone flux through open stomata. Our measurements reveal that fast ozone loss at the plant surface is accompanied with prompt release of oxygenated volatile compounds. In the ozone fumigation experiments of different Nicotiana tabacum varieties the release of specific volatile oxy-VOCs allowed to identify the semi volatile precursor compounds at the plant surface. Ozone fumigation experiments with Norway spruce (Picea abies) and Scots Pine (Pinus sylvestris), two common species in the Northern Hemisphere, show also a significant ozone loss at the plant surface for Picea abies. Fluid dynamic calculations of ozone transport in the diffusive leaf boundary layer reveal a vertical but no horizontal ozone gradient thus reducing ozone fluxes through the pores in case of efficient ozone scavenging plant surfaces. We explain this efficient ozone protection mechanism by the porous surface architecture of plants in combination with unsaturated semi-volatile compounds deposited at the plant surface. These results show that unsaturated semi-volatile compounds at the plant surface should be considered as oxygenated VOC source, impacting gas phase chemistry, as well as efficient ozone sink improving the plant's ozone tolerance

  2. Nanochemistry – Chemical Reactions of Iron and Benzene Within Molecular Clusters

    Microsoft Academic Search

    C. S. Feigerle; S. Bililign; John C. Miller

    2000-01-01

    Molecular clusters represent a nanoscale test tube where chemical reactions can be examined in a unique way for the effects of the local environment and the possibility of size-dependent reactions. Previous experiments have shown that the ionization\\/dissociation of iron pentacarbonyl clusters can lead to the formation of iron ions and iron cluster ions and that these species can further react

  3. Method and apparatus for controlling gas evolution from chemical reactions

    Microsoft Academic Search

    James R. Skorpik; Michael G. Dodson

    1999-01-01

    The present invention is directed toward monitoring a thermally driven gas evolving chemical reaction with an acoustic apparatus. Signals from the acoustic apparatus are used to control a heater to prevent a run-away condition. A digestion module in combination with a robotic arm further automate physical handling of sample material reaction vessels. The invention is especially useful for carrying out

  4. Restricted cooperative games on metabolic networks reveal functionally important reactions.

    PubMed

    Sajitz-Hermstein, Max; Nikoloski, Zoran

    2012-12-01

    Understanding the emerging properties of complex biological systems is in the crux of systems biology studies. Computational methods for elucidating the role of each component in the synergetic interplay can be used to identify targets for genetic and metabolic engineering. In particular, we aim at determining the importance of reactions in a metabolic network with respect to a specific biological function. Therefore, we propose a novel game-theoretic framework which integrates restricted cooperative games with the outcome of flux balance analysis. We define productivity games on metabolic networks and present an analysis of their unrestricted and restricted variants based on the game-theoretic solution concept of the Shapley value. Correspondingly, this concept provides a characterization of the robustness and functional centrality for each enzyme involved in a given metabolic network. Furthermore, the comparison of two different environments - feast and famine - demonstrates the dependence of the results on the imposed flux capacities. PMID:22940237

  5. Mass Accommodation and Chemical Reaction at Gas-Liquid Interfaces

    NASA Astrophysics Data System (ADS)

    Kolb, C. E.; Williams, L. R.; Jayne, J. T.; Worsnop, D. R.; Davidovits, P.

    2006-12-01

    The uptake of trace gases by liquid surfaces is an important process that initiates the heterogeneous chemistry of liquid aerosol particles and cloud droplets. We have recently reviewed the available experimental data for liquid aqueous and aqueous/organic surfaces (1). The review highlights some inconsistencies among experimental results and between experimental results and molecular dynamics simulations. Some of these inconsistencies will be evaluated and discussed in terms of the physics of liquid interfaces, the limitations of various experimental techniques and the disparate scales of laboratory experiments and current molecular simulations (1, 2). 1. Davidovits, P., Kolb, C. E., Williams, L. R., Jayne, J. T., Worsnop, D. R., 2006, Mass Accommodation and Chemical Reactions at Gas Liquid Interfaces, Chem. Rev. 106, 1323-1354. 2. Garrett, B. C., Schenter, G. K., Morita, A., 2006, Molecular Simulations of Molecules across the Liquid/Vapor Interface of Water, Chem. Rev. 106, 1355-1374.

  6. Cu-free click cycloaddition reactions in chemical biology†

    PubMed Central

    Jewett, John C.

    2010-01-01

    Bioorthogonal chemical reactions are paving the way for new innovations in biology. These reactions possess extreme selectivity and biocompatibility, such that their participating reagents can form covalent bonds within richly functionalized biological systems—in some cases, living organisms. This tutorial review will summarize the history of this emerging field, as well as recent progress in the development and application of bioorthogonal copper-free click cycloaddition reactions. PMID:20349533

  7. Stochastic Chemical Reactions in Micro-domains

    Microsoft Academic Search

    D. Holcman; Z. Schuss

    2004-01-01

    Traditional chemical kinetics may be inappropriate to describe chemical\\u000areactions in micro-domains involving only a small number of substrate and\\u000areactant molecules. Starting with the stochastic dynamics of the molecules, we\\u000aderive a master-diffusion equation for the joint probability density of a\\u000amobile reactant and the number of bound substrate in a confined domain. We use\\u000athe equation to calculate

  8. A Modular Three-Dimensional Transport Model for Simulation of Advection, Dispersion and Chemical Reaction

    E-print Network

    Zheng, Chunmiao

    and Chemical Reaction of Contaminants in Groundwater Systems By C. Zheng S.S. Papadopulos & Associates, Inc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 7 2.5 CHEMICAL REACTIONS

  9. Computed potential energy surfaces for chemical reactions

    NASA Technical Reports Server (NTRS)

    Heinemann, K.; Walch, Stephen P.

    1992-01-01

    The work on the NH + NO system which was described in the last progress report was written up and a draft of the manuscript is included in the appendix. The appendix also contains a draft of a manuscript on an Ar + H + H surface. New work which was completed in the last six months includes the following: (1) calculations on the (1)CH2 + H2O, H2 + HCOH, and H2 + H2CO product channels in the CH3 + OH reaction; (2) calculations for the NH2 + O reaction; (3) calculations for the CH3 + O2 reaction; and (4) calculations for CH3O and the two decomposition channels--CH2OH and H + H2CO. Detailed descriptions of this work will be given in manuscripts; however, brief descriptions of the CH3 + OH and CH3 + O2 projects are given.

  10. Results of the 2010 Survey on Teaching Chemical Reaction Engineering

    ERIC Educational Resources Information Center

    Silverstein, David L.; Vigeant, Margot A. S.

    2012-01-01

    A survey of faculty teaching the chemical reaction engineering course or sequence during the 2009-2010 academic year at chemical engineering programs in the United States and Canada reveals change in terms of content, timing, and approaches to teaching. The report consists of two parts: first, a statistical and demographic characterization of the…

  11. Influence of trace impurities on chemical reaction hazards

    Microsoft Academic Search

    J. L. Gustin

    2002-01-01

    The influence of trace impurities is frequently mentioned as a possible or probable cause of accidents in the chemical industry. In process conditions where there is a potential for a fast exothermic decomposition or polymerisation reaction, the contamination of pure chemicals by trace impurities may cause problems. Typical examples of this situation are described concerning the processing of organic nitrocompounds

  12. Effect of Finite-rate Chemical Reactions on Turbulence in Hypersonic Turbulent Boundary Layers

    E-print Network

    Martín, Pino

    Effect of Finite-rate Chemical Reactions on Turbulence in Hypersonic Turbulent Boundary Layers Lian reaction. The influence of chemical reactions on temperature fluctuation variance, Reynolds stresses that the recombination reaction enhances turbulence, while the dissociation reaction damps turbulence. Chemical reactions

  13. Basics of Chemical Kinetics -1 Rate of reaction = rate of disappearance of A =

    E-print Network

    Albert, Réka

    Basics of Chemical Kinetics - 1 Rate of reaction = rate of disappearance of A = # of moles of Chemical Kinetics - 3 Elementary Reaction: Reaction order of each species is identical reactions: Forward Reaction Backward Reaction CBA + 2 CBA + 2 CBA + 2 CBA + 2 #12;Basics of Chemical

  14. Analysis of the Reaction Rate Coefficients for Slow Bimolecular Chemical Reactions

    E-print Network

    Kremer, Gilberto M

    2012-01-01

    Simple bimolecular reactions $A_1+A_2\\rightleftharpoons A_3+A_4$ are analyzed within the framework of the Boltzmann equation in the initial stage of a chemical reaction with the system far from chemical equilibrium. The Chapman-Enskog methodology is applied to determine the coefficients of the expansion of the distribution functions in terms of Sonine polynomials for peculiar molecular velocities. The results are applied to the reaction $H_2+Cl\\rightleftharpoons HCl+H$, and the influence of the non-Maxwellian distribution and of the activation-energy dependent reactive cross sections upon the forward and reverse reaction rate coefficients are discussed.

  15. Photochemical reactions of anthropogenic chemicals in seawater

    Microsoft Academic Search

    A. P. Toole; D. G. Crosby

    1988-01-01

    Sunlight-driven, photochemical reactions can be a major degradative force for anthropogenic organic compounds in the aquatic environment. Chlorinated phenols, various classes of pesticides, and polycyclic aromatic hydrocarbons are among some examples of the compounds shown to be degraded by sunlight. Most environmental photochemistry has been studied in fresh water, despite the fact that the oceans cover more than 70% of

  16. ReactionMap: an efficient atom-mapping algorithm for chemical reactions.

    PubMed

    Fooshee, David; Andronico, Alessio; Baldi, Pierre

    2013-11-25

    Large databases of chemical reactions provide new data-mining opportunities and challenges. Key challenges result from the imperfect quality of the data and the fact that many of these reactions are not properly balanced or atom-mapped. Here, we describe ReactionMap, an efficient atom-mapping algorithm. Our approach uses a combination of maximum common chemical subgraph search and minimization of an assignment cost function derived empirically from training data. We use a set of over 259,000 balanced atom-mapped reactions from the SPRESI commercial database to train the system, and we validate it on random sets of 1000 and 17,996 reactions sampled from this pool. These large test sets represent a broad range of chemical reaction types, and ReactionMap correctly maps about 99% of the atoms and about 96% of the reactions, with a mean time per mapping of 2 s. Most correctly mapped reactions are mapped with high confidence. Mapping accuracy compares favorably with ChemAxon's AutoMapper, versions 5 and 6.1, and the DREAM Web tool. These approaches correctly map 60.7%, 86.5%, and 90.3% of the reactions, respectively, on the same data set. A ReactionMap server is available on the ChemDB Web portal at http://cdb.ics.uci.edu . PMID:24160861

  17. The 1st Law of Thermodynamics in Chemical Reactions

    E-print Network

    I. A. Stepanov

    2000-11-10

    In the previous papers of the author it has been shown that the 1st law of thermodynamics in chemical reactions is the following one: dU=dQ+PdV+SUM In the present paper this theory was developed and it has been shown that the 1st law of thermodynamics in chemical reactions has the following form: dC=-dU+dA and -dU=dQ where dC is the change in the chemical energy, dU is the change in the internal energy. Internal energy is the energy of thermal motion of molecules.

  18. LIGAND: Database of Chemical Compounds and Reactions in Biological Pathways

    NSDL National Science Digital Library

    The Institute for Chemical Research at Kyoto University provides this frequently updated and well-documented database of enzyme reactions. With more than 9,300 entries, the LIGAND Chemical Database includes over 3,700 entries for enzymes (the Enzyme Reaction Database) and 5,600 entries for compounds (Chemical Compound Database). The database is searchable by keyword using DBGET (which supports numerous other databases and gene catalogs as well) and is accompanied by clear instructions. The LIGAND database, updated weekly, may be downloaded via anonymous FTP.

  19. Automatic NMR-Based Identification of Chemical Reaction Types in Mixtures of Co-Occurring Reactions

    PubMed Central

    Latino, Diogo A. R. S.; Aires-de-Sousa, João

    2014-01-01

    The combination of chemoinformatics approaches with NMR techniques and the increasing availability of data allow the resolution of problems far beyond the original application of NMR in structure elucidation/verification. The diversity of applications can range from process monitoring, metabolic profiling, authentication of products, to quality control. An application related to the automatic analysis of complex mixtures concerns mixtures of chemical reactions. We encoded mixtures of chemical reactions with the difference between the 1H NMR spectra of the products and the reactants. All the signals arising from all the reactants of the co-occurring reactions were taken together (a simulated spectrum of the mixture of reactants) and the same was done for products. The difference spectrum is taken as the representation of the mixture of chemical reactions. A data set of 181 chemical reactions was used, each reaction manually assigned to one of 6 types. From this dataset, we simulated mixtures where two reactions of different types would occur simultaneously. Automatic learning methods were trained to classify the reactions occurring in a mixture from the 1H NMR-based descriptor of the mixture. Unsupervised learning methods (self-organizing maps) produced a reasonable clustering of the mixtures by reaction type, and allowed the correct classification of 80% and 63% of the mixtures in two independent test sets of different similarity to the training set. With random forests (RF), the percentage of correct classifications was increased to 99% and 80% for the same test sets. The RF probability associated to the predictions yielded a robust indication of their reliability. This study demonstrates the possibility of applying machine learning methods to automatically identify types of co-occurring chemical reactions from NMR data. Using no explicit structural information about the reactions participants, reaction elucidation is performed without structure elucidation of the molecules in the mixtures. PMID:24551112

  20. Automatic NMR-based identification of chemical reaction types in mixtures of co-occurring reactions.

    PubMed

    Latino, Diogo A R S; Aires-de-Sousa, João

    2014-01-01

    The combination of chemoinformatics approaches with NMR techniques and the increasing availability of data allow the resolution of problems far beyond the original application of NMR in structure elucidation/verification. The diversity of applications can range from process monitoring, metabolic profiling, authentication of products, to quality control. An application related to the automatic analysis of complex mixtures concerns mixtures of chemical reactions. We encoded mixtures of chemical reactions with the difference between the (1)H NMR spectra of the products and the reactants. All the signals arising from all the reactants of the co-occurring reactions were taken together (a simulated spectrum of the mixture of reactants) and the same was done for products. The difference spectrum is taken as the representation of the mixture of chemical reactions. A data set of 181 chemical reactions was used, each reaction manually assigned to one of 6 types. From this dataset, we simulated mixtures where two reactions of different types would occur simultaneously. Automatic learning methods were trained to classify the reactions occurring in a mixture from the (1)H NMR-based descriptor of the mixture. Unsupervised learning methods (self-organizing maps) produced a reasonable clustering of the mixtures by reaction type, and allowed the correct classification of 80% and 63% of the mixtures in two independent test sets of different similarity to the training set. With random forests (RF), the percentage of correct classifications was increased to 99% and 80% for the same test sets. The RF probability associated to the predictions yielded a robust indication of their reliability. This study demonstrates the possibility of applying machine learning methods to automatically identify types of co-occurring chemical reactions from NMR data. Using no explicit structural information about the reactions participants, reaction elucidation is performed without structure elucidation of the molecules in the mixtures. PMID:24551112

  1. Sequential Voronoi diagram calculations using simple chemical reactions

    E-print Network

    Costello, Ben de Lacy; Adamatzky, Andy

    2012-01-01

    In our recent paper [de Lacy Costello et al. 2010] we described the formation of complex tessellations of the plane arising from the various reactions of metal salts with potassium ferricyanide and ferrocyanide loaded gels. In addition to producing colourful tessellations these reactions are naturally computing generalised Voronoi diagrams of the plane. The reactions reported previously were capable of the calculation of three distinct Voronoi diagrams of the plane. As diffusion coupled with a chemical reaction is responsible for the calculation then this is achieved in parallel. Thus an increase in the complexity of the data input does not utilise additional computational resource. Additional benefits of these chemical reactions is that a permanent record of the Voronoi diagram calculation (in the form of precipitate free bisectors) is achieved, so there is no requirement for further processing to extract the calculation results. Previously it was assumed that the permanence of the results was also a potenti...

  2. Symmetry numbers and chemical reaction rates

    Microsoft Academic Search

    Antonio Fernández-Ramos; Benjamin A. Ellingson; Rubén Meana-Pañeda; Jorge M. C. Marques; Donald G. Truhlar

    2007-01-01

    This article shows how to evaluate rotational symmetry numbers for different molecular configurations and how to apply them\\u000a to transition state theory. In general, the symmetry number is given by the ratio of the reactant and transition state rotational\\u000a symmetry numbers. However, special care is advised in the evaluation of symmetry numbers in the following situations: (i)\\u000a if the reaction

  3. Understanding chemical reactions within a generalized Hamilton-Jacobi framework

    E-print Network

    A. S. Sanz; X. Gimenez; J. M. Bofill; S. Miret-Artes

    2009-08-13

    Reaction paths and classical and quantum trajectories are studied within a generalized Hamilton-Jacobi framework, which allows to put on equal footing topology and dynamics in chemical reactivity problems. In doing so, we show how high-dimensional problems could be dealt with by means of Caratheodory plots or how trajectory-based quantum-classical analyses reveal unexpected discrepancies. As a working model, we consider the reaction dynamics associated with a Mueller-Brown potential energy surface, where we focus on the relationship between reaction paths and trajectories as well as on reaction probability calculations from classical and quantum trajectories.

  4. LIGAND: database of chemical compounds and reactions in biological pathways

    PubMed Central

    Goto, Susumu; Okuno, Yasushi; Hattori, Masahiro; Nishioka, Takaaki; Kanehisa, Minoru

    2002-01-01

    LIGAND is a composite database comprising three sections: COMPOUND for the information about metabolites and other chemical compounds, REACTION for the collection of substrate–product relations representing metabolic and other reactions, and ENZYME for the information about enzyme molecules. The current release (as of September 7, 2001) includes 7298 compounds, 5166 reactions and 3829 enzymes. In addition to the keyword search provided by the DBGET/LinkDB system, a substructure search to the COMPOUND and REACTION sections is now available through the World Wide Web (http://www.genome.ad.jp/ligand/). LIGAND may be also downloaded by anonymous FTP (ftp://ftp.genome.ad.jp/pub/kegg/ligand/). PMID:11752349

  5. [Research on chemical reactions during ginseng processing].

    PubMed

    Zhang, Miao; Qin, Kun-Ming; Li, Wei-Dong; Yin, Fang-Zhou; Cai, Hao; Cai, Bao-Chang

    2014-10-01

    As a kind of commonly used traditional Chinese medicine, ginseng has a high reputation at home and abroad. The research of ginseng has been expanded to medicine, pharmacy, biology, food science and other fields, with great achievements in recent years. Ginseng contains ginsenosides, volatile oil, carbohydrates, amino acids, polypeptides, inorganic elements and othser chemical constituents. Each component has extensive physiological activity, and is the base of ginseng's effect. After processing, the complicated changes are taken place in the constituents of ginseng, and some new substances produced. This paper aims to review the studies on chemical constituents and their mechanisms during ginseng processing, and the ideas, methods and the direction of the development of traditional Chinese medicine processing in the future. PMID:25612424

  6. Matrix isolation as a tool for studying interstellar chemical reactions

    NASA Technical Reports Server (NTRS)

    Ball, David W.; Ortman, Bryan J.; Hauge, Robert H.; Margrave, John L.

    1989-01-01

    Since the identification of the OH radical as an interstellar species, over 50 molecular species were identified as interstellar denizens. While identification of new species appears straightforward, an explanation for their mechanisms of formation is not. Most astronomers concede that large bodies like interstellar dust grains are necessary for adsorption of molecules and their energies of reactions, but many of the mechanistic steps are unknown and speculative. It is proposed that data from matrix isolation experiments involving the reactions of refractory materials (especially C, Si, and Fe atoms and clusters) with small molecules (mainly H2, H2O, CO, CO2) are particularly applicable to explaining mechanistic details of likely interstellar chemical reactions. In many cases, matrix isolation techniques are the sole method of studying such reactions; also in many cases, complexations and bond rearrangements yield molecules never before observed. The study of these reactions thus provides a logical basis for the mechanisms of interstellar reactions. A list of reactions is presented that would simulate interstellar chemical reactions. These reactions were studied using FTIR-matrix isolation techniques.

  7. Quantifying chemical reactions by using mixing analysis.

    PubMed

    Jurado, Anna; Vázquez-Suñé, Enric; Carrera, Jesús; Tubau, Isabel; Pujades, Estanislao

    2015-01-01

    This work is motivated by a sound understanding of the chemical processes that affect the organic pollutants in an urban aquifer. We propose an approach to quantify such processes using mixing calculations. The methodology consists of the following steps: (1) identification of the recharge sources (end-members) and selection of the species (conservative and non-conservative) to be used, (2) identification of the chemical processes and (3) evaluation of mixing ratios including the chemical processes. This methodology has been applied in the Besòs River Delta (NE Barcelona, Spain), where the River Besòs is the main aquifer recharge source. A total number of 51 groundwater samples were collected from July 2007 to May 2010 during four field campaigns. Three river end-members were necessary to explain the temporal variability of the River Besòs: one river end-member is from the wet periods (W1) and two are from dry periods (D1 and D2). This methodology has proved to be useful not only to compute the mixing ratios but also to quantify processes such as calcite and magnesite dissolution, aerobic respiration and denitrification undergone at each observation point. PMID:25280248

  8. Shock-Induced Chemical Reactions in Structural Energetic Materials

    NASA Astrophysics Data System (ADS)

    Narayanan, V.; Lu, X.; Hanagud, S.

    2006-07-01

    Various powder mixtures like intermetallic mixtures and mixtures of metals and metal oxides have potential applications as structural energetic materials (SEMs). Technologies of varying the compositions and the powder sizes and their synthesis are being investigated to provide multiple desirable characteristics, like high strength and high energy content. In this paper, we formulate a model for SEMs for their application in shock conditions, in the framework of nonequilibrium thermodynamics and continuum mechanics. A mixture of Al and KClO4 is selected as the example for SEMs. A mixture, pore collapse and chemical reaction model are included. By adapting energy barriers for reaction as a function of temperature, particle size and pressure and introducing a relaxation mechanism in the reaction model, a shock-induced chemical reaction model is developed. The variation of the relaxation mechanism is also modeled. The initiation and propagation of chemical reactions are studied. The time and spatial dependency of chemical reaction on the shock wave conditions are investigated.

  9. An Efficient Chemical Reaction Optimization Algorithm for Multiobjective Optimization.

    PubMed

    Bechikh, Slim; Chaabani, Abir; Said, Lamjed Ben

    2014-10-30

    Recently, a new metaheuristic called chemical reaction optimization was proposed. This search algorithm, inspired by chemical reactions launched during collisions, inherits several features from other metaheuristics such as simulated annealing and particle swarm optimization. This fact has made it, nowadays, one of the most powerful search algorithms in solving mono-objective optimization problems. In this paper, we propose a multiobjective variant of chemical reaction optimization, called nondominated sorting chemical reaction optimization, in an attempt to exploit chemical reaction optimization features in tackling problems involving multiple conflicting criteria. Since our approach is based on nondominated sorting, one of the main contributions of this paper is the proposal of a new quasi-linear average time complexity quick nondominated sorting algorithm; therebymaking our multiobjective algorithm efficient from a computational cost viewpoint. The experimental comparisons against several other multiobjective algorithms on a variety of benchmark problems involving various difficulties show the effectiveness and the efficiency of this multiobjective version in providing a wellconverged and well-diversified approximation of the Pareto front. PMID:25373137

  10. METHODOLOGICAL NOTES: Brusselator — an abstract chemical reaction?

    NASA Astrophysics Data System (ADS)

    Lavrova, Anastasiya I.; Postnikov, E. B.; Romanovsky, Yurii M.

    2009-12-01

    In this paper we consider the Brusselator and the Sel'kov model, which describes the irreversible reaction of glycolysis in the regime of self-sustained oscillations. We show that these two differently constructed models can be reduced to a single equation — a generalized Rayleigh equation. The physical basis for this generality is investigated. The advantages of this equation as a tool for qualitative and quantitative analyses, as well as the similarities and differences of the solutions realized for each of the two concrete models in the cases of almost harmonic and relaxation self-sustained oscillations, are discussed.

  11. Laser cutting with chemical reaction assist

    DOEpatents

    Gettemy, Donald J. (Los Alamos, NM)

    1992-01-01

    A method for cutting with a laser beam where an oxygen-hydrocarbon reaction is used to provide auxiliary energy to a metal workpiece to supplement the energy supplied by the laser. Oxygen is supplied to the laser focus point on the workpiece by a nozzle through which the laser beam also passes. A liquid hydrocarbon is supplied by coating the workpiece along the cutting path with the hydrocarbon prior to laser irradiation or by spraying a stream of hydrocarbon through a nozzle aimed at a point on the cutting path which is just ahead of the focus point during irradiation.

  12. Laser cutting with chemical reaction assist

    DOEpatents

    Gettemy, D.J.

    1992-11-17

    A method is described for cutting with a laser beam where an oxygen-hydrocarbon reaction is used to provide auxiliary energy to a metal workpiece to supplement the energy supplied by the laser. Oxygen is supplied to the laser focus point on the workpiece by a nozzle through which the laser beam also passes. A liquid hydrocarbon is supplied by coating the workpiece along the cutting path with the hydrocarbon prior to laser irradiation or by spraying a stream of hydrocarbon through a nozzle aimed at a point on the cutting path which is just ahead of the focus point during irradiation. 1 figure.

  13. Simulation of chemical reaction equilibria by the reaction ensemble Monte Carlo method: a review†

    Microsoft Academic Search

    C. Heath Turner; John K. Brennan; Martin Lísal; William R. Smith; J. Karl Johnson; Keith E. Gubbins

    2008-01-01

    Understanding and predicting the equilibrium behaviour of chemically reacting systems in highly non-ideal environments is critical to many fields of science and technology, including solvation, nanoporous materials, catalyst design, combustion and propulsion science, shock physics and many more. A method with recent success in predicting the equilibrium behaviour of reactions under non-ideal conditions is the reaction ensemble Monte Carlo method

  14. On the relation between reactions and complexes of (bio)chemical reaction networks

    E-print Network

    Neigenfind, Jost; Nikoloski, Zoran

    2012-01-01

    Robustness of biochemical systems has become one of the central questions in systems biology although it is notoriously difficult to formally capture its multifaceted nature. Maintenance of normal system function depends not only on the stoichiometry of the underlying interrelated components, but also on a multitude of kinetic parameters. Invariant flux ratios, obtained within flux coupling analysis, as well as invariant complex ratios, derived within chemical reaction network theory, can characterize robust properties of a system at steady state. However, the existing formalisms for the description of these invariants do not provide full characterization as they either only focus on the flux-centric or the concentration-centric view. Here we develop a novel mathematical framework which combines both views and thereby overcomes the limitations of the classical methodologies. Our unified framework will be helpful in analyzing biologically important system properties.

  15. VoIume57, ncmber 3 -CAL PHYSICSLEITERS 1 Augst 1978 INFEWRED LASER INDUCED CHEMIC_AL REACTIONS

    E-print Network

    Miller, William H.

    VoIume57, ncmber 3 -CAL PHYSICSLEITERS 1 Augst 1978 INFEWRED LASER INDUCED CHEMIC_AL REACTIONS X)even if the reactants are infrared izctive. It is well-known that an infrared laser can accei- erate chemical reactions state. This letter points out that infrared Iaserscan en- hance chemical reactions even if they are far

  16. 5.0 Application of Chemical Reaction Codes 5.1. Background

    E-print Network

    5.1 5.0 Application of Chemical Reaction Codes 5.1. Background Determination of species analyses of water compositions and a competent chemical reaction model. Computerized chemical reaction that may leach from waste, an understanding of the capabilities and application of chemical reaction models

  17. Using hyperheuristics to improve the determination of the kinetic constants of a chemical reaction in

    E-print Network

    Giménez, Domingo

    Using hyperheuristics to improve the determination of the kinetic constants of a chemical reaction constants of a chemical reaction Kinetic parameters of a chemical reaction are determined with metaheuristic of a chemical reaction that occurs in heterogeneous phase involves the simulation of the processes occurring

  18. Chemical reaction network theory for in-silico biologists Jeremy Gunawardena

    E-print Network

    Gunawardena, Jeremy

    Chemical reaction network theory for in-silico biologists Jeremy Gunawardena Bauer Center@cgr.harvard.edu June 20, 2003 Contents 1 Introduction 1 2 Chemical reaction networks 2 3 Linearity in chemical reaction of a system of nonlinear ODEs. The second is Chemical Reaction Network Theory (CRNT), which establishes

  19. Chemical reactions on solid surfaces of astrophysical interest

    NASA Astrophysics Data System (ADS)

    Biham, Ofer; Pirronello, Valerio; Vidali, Gianfranco

    Observed abundances of chemical species in interstellar clouds can be explained in most cases by reaction schemes involving only species in the gas phase. There is however clear evidence that reactions occurring on the surface of dust grains, helping the formation of key molecules, play a fundamental role into shaping the universe as we see it today. In this chapter we focus our attention on surface reactions on solids and in conditions close to those encountered in interstellar clouds. We will describe how experimental techniques of surface science have been used to study the recombination reaction of hydrogen on interstellar dust grain analogues and the oxidation of carbon monoxide in the interaction of oxygen atoms in water ice layers. Using theoretical methods and computer simulations, we show that it is possible to relate experimental results obtained in the laboratory to actual physical and chemical processes occurring in the interstellar space.

  20. International chemical identifier for reactions (RInChI)

    PubMed Central

    2013-01-01

    The IUPAC International Chemical Identifier (InChI) provides a method to generate a unique text descriptor of molecular structures. Building on this work, we report a process to generate a unique text descriptor for reactions, RInChI. By carefully selecting the information that is included and by ordering the data carefully, different scientists studying the same reaction should produce the same RInChI. If differences arise, these are most likely the minor layers of the InChI, and so may be readily handled. RInChI provides a concise description of the key data in a chemical reaction, and will help enable the rapid searching and analysis of reaction databases. PMID:24152584

  1. Reactions of polymers in supercritical fluids for chemical recycling of waste plastics

    Microsoft Academic Search

    M. Goto; M. Sasaki; T. Hirose

    2006-01-01

    Sub- or supercritical fluids have been focused as reaction media for environmental applications from a view point of green\\u000a chemistry. Chemical recycling of waste plastics is important issue. We have applied reaction in water or organic solvent in\\u000a sub- or supercritical condition to convert polymers into its monomers. Condensed polymers such as polyethylene terephthalate\\u000a or nylon 6 were depolymerized to

  2. Reaction Kinetics and Catalysis Letters, Vol. 1, No. 1, 113-117/1974/ STOCHASTIC SIMULATION OF CHEMICAL REACTION BY

    E-print Network

    Tóth, János

    OF CHEMICAL REACTION BY DIGITAL COMPUTER, I. THE MODEL T. Sipos, 1 j. T6th, 2 and P. l~rdi 1 1. Danube Oil Received November 9, 1972 A stochastic model of complex chemical reactions is outlined. A discrete Markovprocess corresponds to the complex chemical reaction in the model i.e. the concentrations

  3. Molecular-level simulations of chemical reaction equilibrium and diffusion in slit and cylindrical nanopores: model dimerisation reactions

    E-print Network

    Lisal, Martin

    Molecular-level simulations of chemical reaction equilibrium and diffusion in slit and cylindrical study of the effects of confinement on chemical reaction equilibrium and diffusion in both slit nanopores 1. Introduction The behaviour of chemical reactions confined in nanopores is of extensive

  4. Method and apparatus for controlling gas evolution from chemical reactions

    DOEpatents

    Skorpik, J.R.; Dodson, M.G.

    1999-05-25

    The present invention is directed toward monitoring a thermally driven gas evolving chemical reaction with an acoustic apparatus. Signals from the acoustic apparatus are used to control a heater to prevent a run-away condition. A digestion module in combination with a robotic arm further automate physical handling of sample material reaction vessels. The invention is especially useful for carrying out sample procedures defined in EPA Methods SW-846. 8 figs.

  5. Method and apparatus for controlling gas evolution from chemical reactions

    DOEpatents

    Skorpik, James R. (Kennewick, WA); Dodson, Michael G. (Richland, WA)

    1999-01-01

    The present invention is directed toward monitoring a thermally driven gas evolving chemical reaction with an acoustic apparatus. Signals from the acoustic apparatus are used to control a heater to prevent a run-away condition. A digestion module in combination with a robotic arm further automate physical handling of sample material reaction vessels. The invention is especially useful for carrying out sample procedures defined in EPA Methods SW-846.

  6. Common side reactions of the glycosyl donor in chemical glycosylation.

    PubMed

    Christensen, Helle M; Oscarson, Stefan; Jensen, Henrik H

    2015-05-18

    Chemical glycosylation is central to carbohydrate chemistry and is generally recognised as a challenging reaction. This review describes the most reoccurring side reactions of glycosyl donors in glycosylation and how scientists have attempted to explain their observations and in some cases succeeded in solving a particular encountered problem. The topics covered are donor hydrolysis, elimination to form glycals, intermolecular aglycon transfer of thioglycosides and glycosyl imidate rearrangement. PMID:25862946

  7. Waste dissolution with chemical reaction, diffusion and advection

    SciTech Connect

    Chambre, P.L.; Kang, C.H.; Lee, W.W.L.; Pigford, T.H.

    1987-06-01

    This paper extends the mass-transfer analysis to include the effect of advective transport in predicting the steady-state dissolution rate, with a chemical-reaction-rate boundary condition at the surface of a waste form of arbitrary shape. This new theory provides an analytic means of predicting the ground-water velocities at which dissolution rate in a geologic environment will be governed entirely to the chemical reaction rate. As an illustration, we consider the steady-state potential flow of ground water in porous rock surrounding a spherical waste solid. 3 refs., 2 figs.

  8. Toward a Thermodynamic Characterization of Chemical Reaction Networks

    NASA Astrophysics Data System (ADS)

    Cantú, Anselmo García; Nicolis, Gregoire

    2006-01-01

    The relation between the topology of a chemical reaction network and its thermodynamic properties, particularly the energy dissipation patterns, is analyzed. Both regular and complex structures are considered. For networks consisting of linear reactions, this task is analytically accomplished by formulating the network dynamics in terms of the network's connectivity matrix. The thermodynamic effect of nonlinear feedback dynamics on chemical networks is considered in the limits of close to and far away from equilibrium and discussed in connection with the robustness of the response to external disturbances.

  9. Freezing of Spinodal Decompostion by Irreversible Chemical Growth Reaction

    E-print Network

    Michael Schulz; Benjamin Paul

    1998-08-10

    We present a description of the freezing of spinodal decomposition in systems, which contain simultaneous irreversible chemical reactions, in the hydrodynamic limit approximation. From own results we conclude, that the chemical reaction leads to an onset of spinodal decomposition also in the case of an initial system which is completely miscible and can lead to an extreme retardation of the dynamics of the spinodal decomposition, with the probability of a general freezing of this process, which can be experimetally observed in simultaneous IPN formation.

  10. Simulation of chemical reaction dynamics on an NMR quantum computer

    E-print Network

    Lu, Dawei; Xu, Ruixue; Chen, Hongwei; Gong, Jiangbin; Peng, Xinhua; Du, Jiangfeng

    2011-01-01

    Quantum simulation can beat current classical computers with minimally a few tens of qubits and will likely become the first practical use of a quantum computer. One promising application of quantum simulation is to attack challenging quantum chemistry problems. Here we report an experimental demonstration that a small nuclear-magnetic-resonance (NMR) quantum computer is already able to simulate the dynamics of a prototype chemical reaction. The experimental results agree well with classical simulations. We conclude that the quantum simulation of chemical reaction dynamics not computable on current classical computers is feasible in the near future.

  11. Reaction Kinetics and Catalysis Letters, Vol. 1, No. 2/1974/209-213 STOCHASTIC SIMULATION OF CHEMICAL REACTIONS BY

    E-print Network

    Tóth, János

    OF CHEMICAL REACTIONS BY DIGITAL COMPUTER, H. APPLICATIONS T. Sipos1, J.TSth 2 and P. ~.rdi1 1. Danube Oil chemical reactions (especially those of biological interest, e.g. reactions exhibiting oscillationReaction Kinetics and Catalysis Letters, Vol. 1, No. 2/1974/209-213 STOCHASTIC SIMULATION

  12. Computed potential energy surfaces for chemical reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1988-01-01

    The minimum energy path for the addition of a hydrogen atom to N2 is characterized in CASSCF/CCI calculations using the (4s3p2d1f/3s2p1d) basis set, with additional single point calculations at the stationary points of the potential energy surface using the (5s4p3d2f/4s3p2d) basis set. These calculations represent the most extensive set of ab initio calculations completed to date, yielding a zero point corrected barrier for HN2 dissociation of approx. 8.5 kcal mol/1. The lifetime of the HN2 species is estimated from the calculated geometries and energetics using both conventional Transition State Theory and a method which utilizes an Eckart barrier to compute one dimensional quantum mechanical tunneling effects. It is concluded that the lifetime of the HN2 species is very short, greatly limiting its role in both termolecular recombination reactions and combustion processes.

  13. CHARACTERIZATION OF CHEMICALLY MODIFIED HYPERTHERMOPHILIC ENZYMES FOR CHEMICAL SYNTHESES AND BIOREMEDIATION REACTIONS

    EPA Science Inventory

    Research developments in the area of biocatalysis in organic solvents are expected to greatly expand the role of bioprocessing in chemical synthesis, fuel processing, and bioremediation technologies. Many biological transformation reactions of interest to DOE site remediation inv...

  14. Amplitude Equations and Chemical Reaction-Diffusion Systems

    E-print Network

    M. Ipsen; F. Hynne; P. G. Soerensen

    1997-11-03

    The paper discusses the use of amplitude equations to describe the spatio-temporal dynamics of a chemical reaction-diffusion system based on an Oregonator model of the Belousov-Zhabotinsky reaction. Sufficiently close to a supercritical Hopf bifurcation the reaction-diffusion equation can be approximated by a complex Ginzburg-Landau equation with parameters determined by the original equation at the point of operation considered. We illustrate the validity of this reduction by comparing numerical spiral wave solutions to the Oregonator reaction-diffusion equation with the corresponding solutions to the complex Ginzburg-Landau equation at finite distances from the bifurcation point. We also compare the solutions at a bifurcation point where the systems develop spatio-temporal chaos. We show that the complex Ginzburg-Landau equation represents the dynamical behavior of the reaction-diffusion equation remarkably well sufficiently far from the bifurcation point for experimental applications to be feasible.

  15. Direct measurement of the reaction front in chemically amplified photoresists.

    PubMed

    Lin, Eric K; Soles, Christopher L; Goldfarb, Dario L; Trinque, Brian C; Burns, Sean D; Jones, Ronald L; Lenhart, Joseph L; Angelopoulos, Marie; Willson, C Grant; Satija, Sushil K; Wu, Wen-Li

    2002-07-19

    The continuing drive by the semiconductor industry to fabricate smaller structures using photolithography will soon require dimensional control at length scales comparable to the size of the polymeric molecules in the materials used to pattern them. The current technology, chemically amplified photoresists, uses a complex reaction-diffusion process to delineate patterned areas with high spatial resolution. However, nanometer-level control of this critical process is limited by the lack of direct measurements of the reaction front. We demonstrate the use of x-ray and neutron reflectometry as a general method to measure the spatial evolution of the reaction-diffusion process with nanometer resolution. Measuring compositional profiles, provided by deuterium-labeled reactant groups for neutron scattering contrast, we show that the reaction front within the material is broad rather than sharply defined and the compositional profile is altered during development. Measuring the density profile, we directly correlate the developed film structure with that of the reaction front. PMID:12130778

  16. Impact of supersonic and subsonic aircraft on ozone: Including heterogeneous chemical reaction mechanisms

    NASA Technical Reports Server (NTRS)

    Kinnison, Douglas E.; Wuebbles, Donald J.

    1994-01-01

    Preliminary calculations suggest that heterogeneous reactions are important in calculating the impact on ozone from emissions of trace gases from aircraft fleets. In this study, three heterogeneous chemical processes that occur on background sulfuric acid aerosols are included and their effects on O3, NO(x), Cl(x), HCl, N2O5, ClONO2 are calculated.

  17. Reduction of chemical reaction networks through delay distributions

    NASA Astrophysics Data System (ADS)

    Barrio, Manuel; Leier, André; Marquez-Lago, Tatiana T.

    2013-03-01

    Accurate modelling and simulation of dynamic cellular events require two main ingredients: an adequate description of key chemical reactions and simulation of such chemical events in reasonable time spans. Quite logically, posing the right model is a crucial step for any endeavour in Computational Biology. However, more often than not, it is the associated computational costs which actually limit our capabilities of representing complex cellular behaviour. In this paper, we propose a methodology aimed at representing chains of chemical reactions by much simpler, reduced models. The abridgement is achieved by generation of model-specific delay distribution functions, consecutively fed to a delay stochastic simulation algorithm. We show how such delay distributions can be analytically described whenever the system is solely composed of consecutive first-order reactions, with or without additional "backward" bypass reactions, yielding an exact reduction. For models including other types of monomolecular reactions (constitutive synthesis, degradation, or "forward" bypass reactions), we discuss why one must adopt a numerical approach for its accurate stochastic representation, and propose two alternatives for this. In these cases, the accuracy depends on the respective numerical sample size. Our model reduction methodology yields significantly lower computational costs while retaining accuracy. Quite naturally, computational costs increase alongside network size and separation of time scales. Thus, we expect our model reduction methodologies to significantly decrease computational costs in these instances. We anticipate the use of delays in model reduction will greatly alleviate some of the current restrictions in simulating large sets of chemical reactions, largely applicable in pharmaceutical and biological research.

  18. Gas-phase reactions of halogen species of atmospheric importance

    NASA Astrophysics Data System (ADS)

    Heard, Anne C.

    A low-pressure discharge-flow technique, with various optical detection methods, has been used to determine bimolecular rate coefficients for a number of reactions in the gas-phase between OH radicals and organic halogen-containing molecules and between NO3 radicals and the iodine species I2 and I. These experiments have shown that: (1) the reaction of methyl iodide with OH accounts for approximately 2 percent of the removal of CH3I from the troposphere as compared with photolysis; (2) abstraction of I-atoms from a C-I bond by OH is probable in the gas-phase; (3) the halogen-containing anaesthetic substances halothane CF3CClBrH, enflurane CF2HOCF2CFClH, isoflurane CF2HOCClHCF3 and sevoflurane (CF3)2CHOCFH2 have significantly shorter tropospheric lifetimes than the fully halogenated CFCs and halons because of reaction with the OH radical and are thus unlikely to be transported up to the stratosphere where they could contribute to the depletion of ozone. Data obtained for reactions between OH and some 'CFC alternatives' along with measurements of the integrated absorption cross-sections of the compounds in the spectral region 800-1200 cm(exp -1) were used to calculate ozone depletion potentials (ODP) and greenhouse warming potentials relative to CFCl3 for each compound. The study of the reactions between OH and CF3CFBrH and CF2BrH was used to provide a useful first estimate of the environmental acceptability of these compounds in the context of their possible use as replacements for the conventional CFCs. A method was developed to provide a first estimate of the ODP of a halogenated alkane without use of a complicated (and expensive) computer modeling scheme. A reaction between molecular iodine and the nitrate radical in the gas-phase was discovered and the kinetics of this reaction have been studied. No temperature or pressure dependence was observed for the rate of reaction, the rate constant of which was found to be (1.5 +/- 0.5) x 10(exp -12)/cu cm/molecule/s. The reaction between I and NO3 was found to occur at a rate of about 60 percent of the hard-sphere collision frequency for the two species. The rate constant for reaction between I and NO3 was found to be (4.5 +/- 1.9) x 10(exp -10)/cu cm/molecule/s. An upper limit for the heat of formation of IONO2 of (21 +/- 3) kJmol(exp -1) was also derived.

  19. Program Helps To Determine Chemical-Reaction Mechanisms

    NASA Technical Reports Server (NTRS)

    Bittker, D. A.; Radhakrishnan, K.

    1995-01-01

    General Chemical Kinetics and Sensitivity Analysis (LSENS) computer code developed for use in solving complex, homogeneous, gas-phase, chemical-kinetics problems. Provides for efficient and accurate chemical-kinetics computations and provides for sensitivity analysis for variety of problems, including problems involving honisothermal conditions. Incorporates mathematical models for static system, steady one-dimensional inviscid flow, reaction behind incident shock wave (with boundary-layer correction), and perfectly stirred reactor. Computations of equilibrium properties performed for following assigned states: enthalpy and pressure, temperature and pressure, internal energy and volume, and temperature and volume. Written in FORTRAN 77 with exception of NAMELIST extensions used for input.

  20. Network Theory II: Stochastic Petri Nets, Chemical Reaction Networks

    E-print Network

    Baez, John

    inverses! So, we only evolve forwards in time in stochastic physics. #12;Suppose we have a Petri netNetwork Theory II: Stochastic Petri Nets, Chemical Reaction Networks and Feynman Diagrams John Baez, Jacob Biamonte, Brendan Fong #12;A Petri net is a way of drawing a finite set S of species, a finite set

  1. A chemical reaction-based boundary condition for flow electrification

    Microsoft Academic Search

    A. P. Washabaugh; M. Zahn

    1997-01-01

    A physical model is developed for the charge transfer boundary condition in semi-insulating liquids. The boundary condition is based upon interfacial chemical reactions and extends established relations for the interface by including the effects of interfacial surface charge and charge desorption at the interface. A steady state model for flow electrification in a rotating cylindrical electrode apparatus incorporated this boundary

  2. Chemical etching of manganese oxides for electrocatalytic oxygen reduction reaction.

    PubMed

    Lei, Kaixiang; Han, Xiaopeng; Hu, Yuxiang; Liu, Xue; Cong, Liang; Cheng, Fangyi; Chen, Jun

    2015-07-25

    Mixed-valent MnOx (1 < x < 2) was selectively synthesized by chemically etching MnO and Mn2O3 with ceric ammonium nitrate. The obtained MnOx exhibited greatly enhanced electrocatalytic activity toward the oxygen reduction reaction (ORR) as compared to the corresponding pristine oxides. PMID:26097914

  3. Chemical reaction models for non-equilibrium phase transitions

    Microsoft Academic Search

    F. Schlögl

    1972-01-01

    Chemical model reactions are discussed the steady states of which show the phenomenon of non equilibrium phase transitions. One example shows a phase transition of second order, another one shows a phase transition of first order. If diffusion occurs in the case of first order transition, coexistence of two phases in different domains is possible. For plane boundary layers between

  4. Interaction between chemical reactions and mixing on various scales

    Microsoft Academic Search

    S. J. Hearn

    1997-01-01

    The way in which reagents are mixed can have a large influence on the product distribution of a chemical reaction. This has been analysed earlier when micromixing is the limiting mixing step. Additional segregation at a larger scale has only been treated in detail when the local turbulent dispersion of a feed stream was relevant. Here additional segregation due to

  5. Pyrimidine-specific chemical reactions useful for DNA sequencing.

    PubMed Central

    Rubin, C M; Schmid, C W

    1980-01-01

    Potassium permanganate reacts selectively with thymidine residues in DNA (1) while hydroxylamine hydrochloride at pH 6 specifically attacks cytosine (2). We have adopted these reactions for use with the chemical sequencing method developed by Maxam and Gilbert (3). Images PMID:7443522

  6. Fabrication of superhydrophobic copper by wet chemical reaction

    Microsoft Academic Search

    Zhiguang Guo; Jian Fang; Libo Wang; Weimin Liu

    2007-01-01

    A wet chemical reaction was employed herein to fabricate a stable superhydrophobic surface on a polished copper substrate at ambient temperature. The resulting surface showed superhydrophobic properties as evidenced by a water contact angle (CA) of about 154° and a water sliding angle (SA) of about 4°, which may be attributed to the combination of the roughened surface morphology by

  7. Dissipation Scale Fluctuations and Chemical Reaction Rates in Turbulent Flows

    E-print Network

    Victor Yakhot

    2007-06-29

    Small separation between reactants, not exceeding $10^{-8}-10^{-7}cm$, is the necessary condition for various chemical reactions. It is shown that random advection and stretching by turbulence leads to formation of scalar-enriched sheets of {\\it strongly fluctuating thickness} $\\eta_{c}$. The molecular-level mixing is achieved by diffusion across these sheets (interfaces) separating the reactants. Since diffusion time scale is $\\tau_{d}\\propto \\eta_{c}^{2}$, the knowledge of probability density $Q(\\eta_{c},Re)$ is crucial for evaluation of chemical reaction rates. In this paper we derive the probability density $Q(\\eta_{c},Re,Sc)$ and predict a transition in the reaction rate behavior from ${\\cal R}\\propto \\sqrt{Re}$ ($Re\\leq 10^{4}$) to the high-Re asymptotics ${\\cal R}\\propto Re^{0}$. The theory leads to an approximate universality of transitional Reynolds number $Re_{tr}\\approx 10^{4}$. It is also shown that if chemical reaction involves short-lived reactants, very strong anomalous fluctuations of the length-scale $\\eta_{c}$ may lead to non-negligibly small reaction rates.

  8. Students' Understandings of Chemical Bonds and the Energetics of Chemical Reactions.

    ERIC Educational Resources Information Center

    Boo, Hong Kwen

    1998-01-01

    Investigates Grade 12 students' understandings of the nature of chemical bonds and the energetics elicited across five familiar chemical reactions following a course of instruction. Discusses the many ways in which students can misconstruct concepts and principles. Contains 63 references. (DDR)

  9. Identification of responsible volatile chemicals that induce hypersensitive reactions to multiple chemical sensitivity patients

    Microsoft Academic Search

    Naohide Shinohara; Atsushi Mizukoshi; Yukio Yanagisawa

    2004-01-01

    Multiple chemical sensitivity (MCS) has become a serious problem as a result of airtight techniques in modern construction. The mechanism of the MCS, however, has not been clarified. Responsible chemicals and their exposure levels for patient's hypersensitive reactions need to be identified. We measured the exposure of 15 MCS patients to both carbonyl compounds and volatile organic compounds (VOCs) that

  10. Development of a chemical oxygen - iodine laser with production of atomic iodine in a chemical reaction

    SciTech Connect

    Censky, M; Spalek, O; Jirasek, V; Kodymova, J [Institute of Physics, Czech Academy of Sciences, Prague (Czech Republic); Jakubec, I [Institute of Inorganic Chemistry, Czech Academy of Sciences, Rez (Czech Republic)

    2009-11-30

    The alternative method of atomic iodine generation for a chemical oxygen - iodine laser (COIL) in chemical reactions with gaseous reactants is investigated experimentally. The influence of the configuration of iodine atom injection into the laser cavity on the efficiency of the atomic iodine generation and small-signal gain is studied. (lasers)

  11. Theoretical Chemical Dynamics Studies of Elementary Combustion Reactions

    SciTech Connect

    Donald L. Thompson

    2006-04-27

    The purpose of this research was the development and application of theoretical/computational methods for accurate predictions of the rates of reactions in many-atom systems. The specific aim was to improve computational methods for studying the chemical dynamics of large, complex systems and to obtain a better understanding of the chemical reactions involving large polyatomic molecules and radicals. The focus was on the development an automatic potential energy surface generation algorithm that takes advantage of high-performance computing environments; e.g., software for rate calculations that direct quantum chemistry codes to produce ab initio predictions of reaction rates and related dynamics quantities. Specifically, we developed interpolative moving least-squares (IMLS) methods for accurately fitting ab initio energies to provide global PESs and for use in direct dynamics simulations.

  12. Reaction driven convection around a stably stratified chemical front.

    PubMed

    D'Hernoncourt, J; Zebib, A; De Wit, A

    2006-04-21

    A vertical stratification of a light and hot fluid over a heavy and cold one is expected to be stable with regard to buoyancy-driven convection. Here we show that chemical reactions can trigger convection around chemical fronts even in cases where concentration and heat both contribute to a stable density stratification. The balance between intrinsic thermal and solutal density gradients initiated by a spatially localized reaction zone and double diffusive mechanisms are at the origin of a new convective instability, the mechanism of which is explained by a displaced particle argument. Linear stability analysis of a reaction-diffusion-convection model confirmed by nonlinear simulations delimits the instability region in the parameter space spanned by the thermal and solutal Rayleigh numbers. Experimental systems in which to test our theoretical predictions are proposed. PMID:16712159

  13. The Structure and Chemistry of Solid Surfaces The structure of solid surfaces and the chemical reactions that take place on surfaces are of fundamental

    E-print Network

    Ben-Arie, Jezekiel

    reactions that take place on surfaces are of fundamental importance to a wide variety of technological surfaces as well as the chemical reactions that take place on the surfaces of metals and metal oxides.[1 on a project exploring surface chemical reactions related to problems in heterogeneous catalysis. This project

  14. Moment equations for chemical reactions on interstellar dust grains

    E-print Network

    Azi Lipshtat; Ofer Biham

    2002-12-09

    While most chemical reactions in the interstellar medium take place in the gas phase, those occurring on the surfaces of dust grains play an essential role. Chemical models based on rate equations including both gas phase and grain surface reactions have been used in order to simulate the formation of chemical complexity in interstellar clouds. For reactions in the gas phase and on large grains, rate equations, which are highly efficient to simulate, are an ideal tool. However, for small grains under low flux, the typical number of atoms or molecules of certain reactive species on a grain may go down to order one or less. In this case the discrete nature of the opulations of reactive species as well as the fluctuations become dominant, thus the mean-field approximation on which the rate equations are based does not apply. Recently, a master equation approach, that provides a good description of chemical reactions on interstellar dust grains, was proposed. Here we present a related approach based on moment equations that can be obtained from the master equation. These equations describe the time evolution of the moments of the distribution of the population of the various chemical species on the grain. An advantage of this approach is the fact that the production rates of molecular species are expressed directly in terms of these moments. Here we use the moment equations to calculate the rate of molecular hydrogen formation on small grains. It is shown that the moment equation approach is efficient in this case in which only a single reactive specie is involved. The set of equations for the case of two species is presented and the difficulties in implementing this approach for complex reaction networks involving multiple species are discussed.

  15. Capture of spatially homogeneous chemical reactions in tissue by freezing.

    PubMed Central

    Clark, A; Clark, P A

    1983-01-01

    A useful technique in studying the saturation of hemoglobin in erythrocytes or myoglobin in tissue is cryophotometry, in which tissue is frozen for later spectrophotometric analysis. A general question associated with this technique is whether the freezing process alters the chemical state. This paper presents a theoretical analysis of the simplest model relevant to that question. We study the effect of rapid cooling on a spatially homogeneous chemical reaction. The analysis shows that changes during freezing are negligible near the boundary to which the heat sink is applied, but can be significant deeper in the sample. The distance from the boundary at which the changes during freezing become appreciable can be expressed simply in terms of the chemical reaction rates and the thermal diffusivity of the tissue. Detailed results are given for the case of oxygen and myoglobin in skeletal muscle. PMID:6838980

  16. Automated Discovery of Elementary Chemical Reaction Steps Using Freezing String and Berny Optimization Methods

    E-print Network

    Suleimanov, Yury V

    2015-01-01

    We present a simple protocol which allows fully automated discovery of elementary chemical reaction steps using in cooperation single- and double-ended transition-state optimization algorithms - the freezing string and Berny optimization methods, respectively. To demonstrate the utility of the proposed approach, the reactivity of several systems of combustion and atmospheric chemistry importance is investigated. The proposed algorithm allowed us to detect without any human intervention not only "known" reaction pathways, manually detected in the previous studies, but also new, previously "unknown", reaction pathways which involve significant atom rearrangements. We believe that applying such a systematic approach to elementary reaction path finding will greatly accelerate the possibility of discovery of new chemistry and will lead to more accurate computer simulations of various chemical processes.

  17. Chemical reactions studied at ultra-low temperature in liquid helium clusters

    SciTech Connect

    Huisken, Friedrich; Krasnokutski, Serge A. [Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the University of Jena, Institute of Solid State Physics, Helmholtzweg 3, D-07743 Jena (Germany)

    2012-11-27

    Low-temperature reaction rates are important ingredients for astrophysical reaction networks modeling the formation of interstellar matter in molecular clouds. Unfortunately, such data is difficult to obtain by experimental means. In an attempt to study low-temperature reactions of astrophysical interest, we have investigated relevant reactions at ultralow temperature in liquid helium droplets. Being prepared by supersonic expansion of helium gas at high pressure through a nozzle into a vacuum, large helium clusters in the form of liquid droplets constitute nano-sized reaction vessels for the study of chemical reactions at ultra-low temperature. If the normal isotope {sup 4}He is used, the helium droplets are superfluid and characterized by a constant temperature of 0.37 K. Here we present results obtained for Mg, Al, and Si reacting with O{sub 2}. Mass spectrometry was employed to characterize the reaction products. As it may be difficult to distinguish between reactions occurring in the helium droplets before they are ionized and ion-molecule reactions taking place after the ionization, additional techniques were applied to ensure that the reactions actually occurred in the helium droplets. This information was provided by measuring the chemiluminescence light emitted by the products, the evaporation of helium atoms by the release of the reaction heat, or by laser-spectroscopic identification of the reactants and products.

  18. INVESTIGATION OF IMPORTANT HYDROXYL RADICAL REACTIONS IN THE PERTURBED TROPOSPHERE

    EPA Science Inventory

    The flash-photolysis resonance fluorescence technique was used to study the reaction kinetics of hydroxyl radicals with ten aromatic and six olefinic hydrocarbons at 298 K and several diluent gas pressures. The aromatic compounds that were studied include benzene, toluene, ethylb...

  19. Gas-Phase Reactions of Halogen Species of Atmospheric Importance.

    NASA Astrophysics Data System (ADS)

    Heard, Anne C.

    Available from UMI in association with The British Library. Requires signed TDF. A low-pressure discharge-flow technique, with various optical detection methods, has been used to determine bimolecular rate coefficients for a number of reactions in the gas-phase between OH radicals and organic halogen -containing molecules and between NO_3 radicals and the iodine species I_2 and I. These experiments have shown that: (i) the reaction of methyl iodide with OH accounts for approximately 2% of the removal of CH_3I from the troposphere as compared with photolysis; (ii) abstraction of I-atoms from a C-I bond by OH is probable in the gas -phase; (iii) the halogen-containing anaesthetic substances halothane CF_3CCl BrH, enflurane CF_2HOCF _2CFClH, isoflurane CF_2HOCClHCF _3 and sevoflurane (CF_3) _2CHOCFH_2 have significantly shorter tropospheric lifetimes than the fully halogenated CFCs and halons because of reaction with the OH radical and are thus unlikely to be transported up to the stratosphere where they could contribute to the depletion of ozone. Data obtained for reactions between OH and some 'CFC alternatives' along with measurements of the integrated absorption cross -sections of the compounds in the spectral region 800-1200 cm^{-1} were used to calculate ozone depletion potentials (ODP) and greenhouse warming potentials relative to CFCl_3 for each compound. The study of the reactions between OH and CF_3CFBrH and CF _2BrH was used to provide a useful first estimate of the environmental acceptability of these compounds in the context of their possible use as replacements for the conventional CFCs. A method was developed to provide a first estimate of the ODP of a halogenated alkane without use of a complicated (and expensive) computer modeling scheme. A reaction between molecular iodine and the nitrate radical in the gas-phase was discovered and the kinetics of this reaction have been studied. No temperature or pressure dependence was observed for the rate of reaction, the rate constant of which was found to be (1.5 +/- 0.5) times 10 ^{-12}cm^{ -3}molecule^{-1}s ^{-1}. The reaction between I and NO_3 was found to occur at a rate of about 60% of the hard-sphere collision frequency for the two species. The rate constant for reaction between I and NO_3 was found to be (4.5 +/- 1.9) times 10^{-10}cm^3 molecule^{-1}s ^{-1}. An upper limit for the heat of formation of IONO_2 of (21 +/- 3) kJmol^ {-1} was also derived. (Abstract shortened by UMI.).

  20. Modelling of gas-solid reaction—Coupling of heat and mass transfer with chemical reaction

    Microsoft Academic Search

    Hui-Bo Lu; Nathalie Mazet; Bernard Spinner

    1996-01-01

    A general gas-solid reaction model is formulated. This work is the further development of the previous modelling work of Mazet (1988, Ph.D. Thesis, University of Perpignan) and Goetz (1991, Ph.D. Thesis, University of Perpignan) to simulate reversible gas-solid reactions that have been extensively applied to the new chemical heat pump technology developed at CNRS-IMP. In the present paper, a general

  1. Accurate hybrid stochastic simulation of a system of coupled chemical or biochemical reactions

    E-print Network

    Minnesota, University of

    Accurate hybrid stochastic simulation of a system of coupled chemical or biochemical reactions reactions, approximates the fast reactions as a continuous Markov process, using a chemical Langevin multiple slow reactions may occur within a time step of the numerical integration of the chemical Langevin

  2. "Kinetics of Chemical Reactions in Environmental Systems: Research Needs and Challenges"

    E-print Network

    Sparks, Donald L.

    "Kinetics of Chemical Reactions in Environmental Systems: Research Needs and Challenges" Donald(oid)s, nutrients, radionuclides, and organic chemicals have shown that reaction rates are initially rapid followed by a slow approach to a steady state. The rapid reaction has been ascribed to chemical reactions and film

  3. Journal of Mathematical Chemistry 0 1999 ? ? 1 Chemical Clock Reactions: The E ect of Precursor

    E-print Network

    Billingham, John

    Journal of Mathematical Chemistry 0 1999 ? ? 1 Chemical Clock Reactions: The E ect of Precursor reaction is a chemical reaction which gives rise to a signi cant in- duction period during which one increases, for example cubic autocatal- #12;2 S. J. Preece et al Chemical Clock Reactions ysis: A + 2B ,! 3B

  4. Extinction and Spread of Isothemal Flame Balls in An Autocatalytic Chemical Reaction

    E-print Network

    Shi, Jun-Ping

    Extinction and Spread of Isothemal Flame Balls in An Autocatalytic Chemical Reaction Junping Shi: reaction rate Reaction-diffusion system of chemical reaction: a t = DAa - kabp, b t = DBb + kabp, t > 0, x(?). Remember that there are more than 4000 universities in USA! #12;An isothermal autocatalytic chemical

  5. 227-0684-00L Control Methods in Systems Biology May 12, 2011 Lecture 10: Chemical Reaction Network Theory (CRNT)

    E-print Network

    Lygeros, John

    227-0684-00L Control Methods in Systems Biology May 12, 2011 Lecture 10: Chemical Reaction Network's lecture · Stochastic simulation ­ Mass (moiety) conservation · Chemical reaction network theory ­ Chemical kinetics ­ Definitions central to chemical reaction network theory ­ Nonnegativity ­ Deficiency Zero

  6. Chemical reaction of metal-fullerene in gas phase (2) >Masamichi Konoa

    E-print Network

    Maruyama, Shigeo

    f18-068 Chemical reaction of metal-fullerene in gas phase (2) ·>Masamichi Konoa , Syuhei Inoueb structure, formation mechanism, chemical reactivity, and so on. To examine these question, chemical reaction clusters. In order to observe the chemical reaction product on a clean baseline, all clusters except for C

  7. Spatial patterns and double diffusion in chemical reactions

    PubMed Central

    Dewel, G.; Borckmans, P.; Walgraef, D.

    1983-01-01

    Spatial ordering has been observed recently during various photochemical reactions. Convoluted concentration bands first appear near the surface of shallow irradiated solutions. They thereafter extend into the bulk, and finger-like structures spontaneously develop. We discuss here the possible role of double-diffusion effects in the onset of this phenomenon. Indeed, chemical reactions occurring near the surface or evaporation of the solvent, or both, induce in the bulk adverse gradients of a pair of properties (concentrations of solute or concentration and temperature) having different diffusivities. This difference can then destabilize the homogeneous solution and trigger the observed patterns. PMID:16593384

  8. Tailoring oxidation degrees of graphene oxide by simple chemical reactions

    SciTech Connect

    Wang Gongkai [Key Laboratory for Anisotropy and Texture of Materials of Ministry of Education, Northeastern University, Shenyang, Liaoning 110004 (China); Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Sun Xiang; Lian Jie [Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Liu Changsheng [Key Laboratory for Anisotropy and Texture of Materials of Ministry of Education, Northeastern University, Shenyang, Liaoning 110004 (China)

    2011-08-01

    High quality graphene oxide (GO) with controllable degrees of oxidation was synthesized by simple chemical reactions inspired by approaches to unzip single wall carbon nanotubes using strong oxidizing agents. As compared to the conventional Hummers method, these reactions are less exo-therm involved without emission of toxic gases. The structural characteristics of the synthesized GO with various oxidation degrees were evaluated by x-ray diffraction, x-ray photoelectron spectroscopy, Raman spectroscopy, thermal gravimetric analysis, and UV-vis-IR spectroscopy. GO with tailored degrees of oxidation displays tunable optoelectronic properties and may have a significant impact on developing graphene- or GO-based platforms for various technological applications.

  9. Potential for exothermic chemical reactions in waste tanks

    SciTech Connect

    Van Tuyl, H.H.

    1983-02-03

    The potential for exothermic chemical reactions in waste tanks at Hanford is discussed. Organic chemicals have been added to Hanford waste tanks, particularly as ferrocyanides and when processing sludges at B Plant. Recent planned or ongoing activities involving stored wastes have possibly increased the potential for reaction of these wastes with nitrate salts in the waste tanks. Risk evaluations appear to be deficient in assessing the consequences of a deflagration, and in determining the probability of either a deflagration or detonation. The present question is whether current plans and recent safety-related documentation have given proper consideration to the available information about organic compounds in waste tanks. The principal organic additions to Hanford waste tanks are 1200 tonnes of organic carbon'' and 500 tonnes of Ni{sub 2}Fe(CN){sub 6}. 13 refs.

  10. Controlling ultracold chemical reactions via Rydberg-dressed interactions

    E-print Network

    Jia Wang; Jason N. Byrd; Ion Simbotin; R. Côté

    2014-03-24

    We show that ultracold chemical reactions can be manipulated and controlled by using Rydberg-dressed interactions. Scattering in the ultracold regime is sensitive to long-range interactions, especially when weakly bound (or quasi-bound) states exist near the collision threshold. We investigate how, by Rydberg-dressing a reactant, one enhances its polarizability and modifies the long-range van der Waals collision complex, which can alter chemical reaction rates by shifting the position of near threshold bound states. We carry out a full quantum mechanical scattering calculation for the benchmark system H$_2$+D, and show that resonances can be moved substantially and that rate coefficients at cold and ultracold temperatures can be increased by several orders of magnitude.

  11. Tuning ultracold chemical reactions via Rydberg-dressed interactions.

    PubMed

    Wang, Jia; Byrd, Jason N; Simbotin, Ion; Côté, R

    2014-07-11

    We show that ultracold chemical reactions with an activation barrier can be tuned using Rydberg-dressed interactions. Scattering in the ultracold regime is sensitive to long-range interactions, especially when weakly bound (or quasibound) states exist near the collision threshold. We investigate how, by Rydberg dressing a reactant, one enhances its polarizability and modifies the long-range van der Waals collision complex, which can alter chemical reaction rates by shifting the position of near-threshold bound states. We carry out a full quantum mechanical scattering calculation for the benchmark system H(2)+D, and show that resonances can be moved substantially and that rate coefficients at cold and ultracold temperatures can be increased by several orders of magnitude. PMID:25062202

  12. Chemical Characterization and Reactivity of Fuel-Oxidizer Reaction Product

    NASA Technical Reports Server (NTRS)

    David, Dennis D.; Dee, Louis A.; Beeson, Harold D.

    1997-01-01

    Fuel-oxidizer reaction product (FORP), the product of incomplete reaction of monomethylhydrazine and nitrogen tetroxide propellants prepared under laboratory conditions and from firings of Shuttle Reaction Control System thrusters, has been characterized by chemical and thermal analysis. The composition of FORP is variable but falls within a limited range of compositions that depend on three factors: the fuel-oxidizer ratio at the time of formation; whether the composition of the post-formation atmosphere is reducing or oxidizing; and the reaction or post-reaction temperature. A typical composition contains methylhydrazinium nitrate, ammonium nitrate, methylammonium nitrate, and trace amounts of hydrazinium nitrate and 1,1-dimethylhydrazinium nitrate. Thermal decomposition reactions of the FORP compositions used in this study were unremarkable. Neither the various compositions of FORP, the pure major components of FORP, nor mixtures of FORP with propellant system corrosion products showed any unusual thermal activity when decomposed under laboratory conditions. Off-limit thruster operations were simulated by rapid mixing of liquid monomethylhydrazine and liquid nitrogen tetroxide in a confined space. These tests demonstrated that monomethylhydrazine, methylhydrazinium nitrate, ammonium nitrate, or Inconel corrosion products can induce a mixture of monomethylhydrazine and nitrogen tetroxide to produce component-damaging energies. Damaging events required FORP or metal salts to be present at the initial mixing of monomethylhydrazine and nitrogen tetroxide.

  13. Implementation of a vibrationally linked chemical reaction model for DSMC

    NASA Technical Reports Server (NTRS)

    Carlson, A. B.; Bird, Graeme A.

    1994-01-01

    A new procedure closely linking dissociation and exchange reactions in air to the vibrational levels of the diatomic molecules has been implemented in both one- and two-dimensional versions of Direct Simulation Monte Carlo (DSMC) programs. The previous modeling of chemical reactions with DSMC was based on the continuum reaction rates for the various possible reactions. The new method is more closely related to the actual physics of dissociation and is more appropriate to the particle nature of DSMC. Two cases are presented: the relaxation to equilibrium of undissociated air initially at 10,000 K, and the axisymmetric calculation of shuttle forebody heating during reentry at 92.35 km and 7500 m/s. Although reaction rates are not used in determining the dissociations or exchange reactions, the new method produces rates which agree astonishingly well with the published rates derived from experiment. The results for gas properties and surface properties also agree well with the results produced by earlier DSMC models, equilibrium air calculations, and experiment.

  14. Quantum chemical analysis of the deferiprone–iron binding reaction

    PubMed Central

    Wiwanitkit, Viroj

    2006-01-01

    To prevent side effects of excessive accumulation of iron in the body, chelation therapy is recommended in transfusion-dependent patients. The reaction between deferiprone and iron to form a complex red substance can be described as 3 molecules of the chelator, deferiprone, reacting with a molecule of iron. However, the actual mechanism of the deferiprone – iron binding reaction is not well understood. A quantum chemical analysis of the deferiprone – iron binding reaction was performed, focusing on the reaction between 1 molecule of deferiprone and 1 molecule of iron. The two main alternative pathways for the deferiprone – iron binding reaction were shown to be C-C cleavage and C-O cleavage. The required energy for complex formation in C-C cleavage was less than for C-O cleavage. The total energy requirement for C-C cleavage was negative, implying that this reaction can occur without any external energy source. The resulting complex fits the reported tertiary structure model for the deferiprone – iron complex PMID:17722270

  15. Stochastic generator of chemical structure. 3. Reaction network generation.

    PubMed

    Faulon, J L; Sault, A G

    2001-01-01

    A new method to generate chemical reaction network is proposed. The particularity of the method is that network generation and mechanism reduction are performed simultaneously using sampling techniques. Our method is tested for hydrocarbon thermal cracking. Results and theoretical arguments demonstrate that our method scales in polynomial time while other deterministic network generators scale in exponential time. This finding offers the possibility of investigating complex reacting systems such as those studied in petroleum refining and combustion. PMID:11500106

  16. Modeling Chemical Reactions with First-Principle Molecular Dynamics

    Microsoft Academic Search

    Artur Michalak; Tom Ziegler

    Density functional theory (DFT)-based molecular dynamics (MD) has established itself as a valuable and powerful tool in studies\\u000a of chemical reactions. Thanks to the rapid increase in power of modern computers, ab initio MD has nowadays become practical. Within the Car-Parinello approach, first-principle MD is already quite popular methodology\\u000a in molecular modeling. MD reveals the dynamical effects at finite temperatures

  17. Stochastic Generator of Chemical Structure. 3. Reaction Network Generation

    SciTech Connect

    FAULON,JEAN-LOUP; SAULT,ALLEN G.

    2000-07-15

    A new method to generate chemical reaction network is proposed. The particularity of the method is that network generation and mechanism reduction are performed simultaneously using sampling techniques. Our method is tested for hydrocarbon thermal cracking. Results and theoretical arguments demonstrate that our method scales in polynomial time while other deterministic network generator scale in exponential time. This finding offers the possibility to investigate complex reacting systems such as those studied in petroleum refining and combustion.

  18. Electric and Magnetic Detection of Avalanche Behavior in Chemical Reactions

    Microsoft Academic Search

    James Claycomb; M. Nersesyan; Martin Miller; John Miller; Dan Luss

    2001-01-01

    Intermittent bursts of chemical activity, displaying avalanche like behavior, have been observed in liquid-solid replacement reactions between metals and liquid electrolytes by measuring the time-dependent electric and magnetic fields. Magnetic measurements are conducted using a high-Tc SQUID inside a magnetically shielded enclosure. Electric potential difference measurements exhibit temporal behavior that is qualitatively similar to the recorded magnetic signals. The observed

  19. Beating polymer gels coupled with a nonlinear chemical reaction

    Microsoft Academic Search

    Ryo Yoshida; Etsuo Kokufuta; Tomohiko Yamaguchi

    1999-01-01

    We report on a beating polymer gel that exhibits periodical volume changes (swelling and deswelling) in a closed solution without external stimuli, like autonomous heartbeat. The mechanical oscillation is driven by the chemical energy of the oscillatory Belousov-Zhabotinsky (BZ) reaction. The gel is a copolymer gel of N-isopropylacrylamide (NIPAAm) in which ruthenium tris(2,2'-bipyridine) [Ru(bpy)3], known as a catalyst of the

  20. Gamma and the Chemical Reaction Model: Fifteen Years After

    Microsoft Academic Search

    Jean-Pierre Ban?tre; Pascal Fradet; Daniel Le Métayer

    Gamma was originally proposed in 1986 as a formalism for the definition of programs without artificial sequentiality. The\\u000a basic idea underlying the formalism is to describe computation as a form of chemical reaction on a collection of individual pieces of data. Due to the very minimal nature of the language, and its absence of sequential\\u000a bias, it has been possible

  1. A microvascular system for chemical reactions using surface waste heat.

    PubMed

    Nguyen, Du Thai; Esser-Kahn, Aaron P

    2013-12-16

    Coffee-powered chemistry: Low-grade waste heat on surfaces can be used to drive chemical reactions, including the regeneration of a CO2 capture solution. Flowing two-phase heat transfer has been implemented within microvascular systems. This stripping system can be adapted to pre-fabricated surfaces, as demonstrated by a coffee mug containing a 1.2?m long microchannel. MEA=monoethanolamine. PMID:24307247

  2. Chemical reactions in viscous liquids under space conditions

    Microsoft Academic Search

    A. Kondyurin; B. Lauke; E. Richter

    2004-01-01

    A long-term human flight needs a large-size space ships with artificial self-regulating ecological life-support system. The best way for creation of large-size space ship is a synthesis of light construction on Earth orbit, that does not need a high energy transportation carriers from Earth surface. The construction can be created by the way of chemical polymerisation reaction under space environment.

  3. STM control of chemical reaction: single-molecule synthesis.

    PubMed

    Hla, Saw-Wai; Rieder, Karl-Heinz

    2003-01-01

    The fascinating advances in single atom/molecule manipulation with a scanning tunneling microscope (STM) tip allow scientists to fabricate atomic-scale structures or to probe chemical and physical properties of matters at an atomic level. Owing to these advances, it has become possible for the basic chemical reaction steps, such as dissociation, diffusion, adsorption, readsorption, and bond-formation processes, to be performed by using the STM tip. Complete sequences of chemical reactions are able to induce at a single-molecule level. New molecules can be constructed from the basic molecular building blocks on a one-molecule-at-a-time basis by using a variety of STM manipulation schemes in a systematic step-by-step manner. These achievements open up entirely new opportunities in nanochemistry and nanochemical technology. In this review, various STM manipulation techniques useful in the single-molecule reaction process are reviewed, and their impact on the future of nanoscience and technology are discussed. PMID:12626735

  4. Exploring complex chemical reactions by ab-initio simulation

    NASA Astrophysics Data System (ADS)

    Parrinello, Michele

    1998-03-01

    Recent progress in the ab-initio molecular dynamics method and the power of parallel computing, allow the detailed study of complex chemical reaction of great industrial relevance. We illustrate this unprecedented capability by investigating the second generation Ziegler-Natta catalytic process. In this inhomogeneous catalyst, a polymerization reaction is induced by TiCl4 molecules deposited on an MgCl2 solid support. A density functional based ab-initio molecular dynamics calculation conducted with a minimum of initial assumption allows to understand the nature of the catalytic center and to determine the reaction path with the associated free energy barrier. Furthermore our calculation can explain in a nontrivial way the stereo-selectivity of the process.

  5. How is entropy production rate related to chemical reaction rate?

    E-print Network

    Banerjee, Kinshuk

    2013-01-01

    The entropy production rate is a key quantity in irreversible thermodynamics. In this work, we concentrate on the realization of entropy production rate in chemical reaction systems in terms of the experimentally measurable reaction rate. Both triangular and linear networks have been studied. They attain either thermodynamic equilibrium or a non-equilibrium steady state, under suitable external constraints. We have shown that the entropy production rate is proportional to the square of the reaction velocity only around equilibrium and not any arbitrary non-equilibrium steady state. This feature can act as a guide in revealing the nature of a steady state, very much like the minimum entropy production principle. A discussion on this point has also been presented.

  6. Printing chemical libraries on microarrays for fluid phase nanoliter reactions

    PubMed Central

    Gosalia, Dhaval N.; Diamond, Scott L.

    2003-01-01

    Chemical compounds within individual nanoliter droplets of glycerol were microarrayed onto glass slides at 400 spots/cm2. Using aerosol deposition, subsequent reagents and water were metered into each reaction center to rapidly assemble diverse multicomponent reactions without crosscontamination or the need for surface linkage. This proteomics technique allowed the kinetic profiling of protease mixtures, protease–substrate interactions, and high-throughput screening reactions. An inhibitor of caspases 2, 4, and 6 was identified by using a 352-compound combinatorial library microarrayed in quadruplicates on 100 slides and screened against caspases 2, 4, and 6, as well as thrombin and chymotrypsin. From one printing run that consumes <1 nanomole of each compound, large combinatorial libraries can be subjected to numerous separation-free homogeneous assays at volumes 103–104 smaller than current high-throughput methods. PMID:12851459

  7. Spatiotemporal regulation of chemical reactions by active cytoskeletal remodeling

    PubMed Central

    Chaudhuri, Abhishek; Bhattacharya, Bhaswati; Gowrishankar, Kripa; Mayor, Satyajit; Rao, Madan

    2011-01-01

    Efficient and reproducible construction of signaling and sorting complexes, both on the surface and within the living cell, is contingent on local regulation of biochemical reactions by the cellular milieu. We propose that in many cases this spatiotemporal regulation can be mediated by interaction with components of the dynamic cytoskeleton. We show how the interplay between active contractility and remodeling of the cytoskeleton can result in transient focusing of passive molecules to form clusters, leading to a dramatic increase in the reaction efficiency and output levels. The dynamic cytoskeletal elements that drive focusing behave as quasienzymes catalyzing the chemical reaction. These ideas are directly applicable to the cortical actin-dependent clustering of cell surface proteins such as lipid-tethered GPI-anchored proteins, Ras proteins, as well as many proteins that have domains that confer the ability to interact with the actin cytoskeleton. In general such cytoskeletal driven clustering of proteins could be a cellular mechanism to spatiotemporally regulate and amplify local chemical reaction rates in a variety of contexts such as signaling, transcription, sorting, and endocytosis. PMID:21873247

  8. Flow Tube Studies of Gas Phase Chemical Processes of Atmospheric Importance

    NASA Technical Reports Server (NTRS)

    Molina, Mario J.

    1998-01-01

    The objective of this project is to conduct measurements of elementary reaction rate constants and photochemical parameters for processes of importance in the atmosphere. These measurements are being carried out under temperature and pressure conditions covering those applicable to the stratosphere and upper troposphere, using the chemical ionization mass spectrometry turbulent flow technique developed in our laboratory. The next section summarizes our research activities during the first year of the project, and the section that follows consists of the statement of work for the third year. Additional details concerning the projects listed in the statement of work were described in our original proposal.

  9. Chapter 3 An Important Well Studied Atmospheric Reaction, O ( D 1 ) + H 2

    Microsoft Academic Search

    João Brandão; Carolina M. A. Rio; Wenli Wang

    2008-01-01

    Among the chemical reactions in atmosphere, the reaction of an excited oxygen atom, O (D1), with ground state molecular hydrogen, H2 (X?g+1), has been one of the most studied both experimentally and theoretically. To describe this reaction, various potential energy surfaces have been calibrated and their dynamics has been studied using quantum mechanical and quasiclassical trajectory methods. The theoretical results

  10. Influence of Chemical Reactions on the Nonlinear Dynamics of Dissipative Flows

    E-print Network

    Karimov, A R; Beklemishev, V V

    2015-01-01

    The nonlinear dynamics of resistive flow with a chemical reaction is studied. Proceeding from the Lagrangian description, the influence of a chemical reaction on the development of fluid singularities is considered.

  11. Influence of Chemical Reactions on the Nonlinear Dynamics of Dissipative Flows

    E-print Network

    A. R. Karimov; A. M. Korshunov; V. V. Beklemishev

    2015-04-16

    The nonlinear dynamics of resistive flow with a chemical reaction is studied. Proceeding from the Lagrangian description, the influence of a chemical reaction on the development of fluid singularities is considered.

  12. Examining the importance of dynamics, barrier compression and hydrogen tunnelling in enzyme catalysed reactions

    Microsoft Academic Search

    Sam Hay; Nigel S. Scrutton

    2011-01-01

    Nuclear quantum mechanical tunnelling is important in enzyme-catalysed H-transfer reactions. This viewpoint has arisen after a number of experimental studies have described enzymatic reactions with kinetic isotope effects that are significantly larger than the semiclassical limit. Other experimental evidence for tunnelling, and the potential role of promoting vibrations that transiently compress the reaction barrier, is more indirect, being derived from

  13. Significance of vapor phase chemical reactions on CVD rates predicted by chemically frozen and local thermochemical equilibrium boundary layer theories

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.

    1988-01-01

    This paper investigates the role played by vapor-phase chemical reactions on CVD rates by comparing the results of two extreme theories developed to predict CVD mass transport rates in the absence of interfacial kinetic barrier: one based on chemically frozen boundary layer and the other based on local thermochemical equilibrium. Both theories consider laminar convective-diffusion boundary layers at high Reynolds numbers and include thermal (Soret) diffusion and variable property effects. As an example, Na2SO4 deposition was studied. It was found that gas phase reactions have no important role on Na2SO4 deposition rates and on the predictions of the theories. The implications of the predictions of the two theories to other CVD systems are discussed.

  14. Physio-chemical reactions in recycle aggregate concrete.

    PubMed

    Tam, Vivian W Y; Gao, X F; Tam, C M; Ng, K M

    2009-04-30

    Concrete waste constitutes the major proportion of construction waste at about 50% of the total waste generated. An effective way to reduce concrete waste is to reuse it as recycled aggregate (RA) for the production of recycled aggregate concrete (RAC). This paper studies the physio-chemical reactions of cement paste around aggregate for normal aggregate concrete (NAC) and RAC mixed with normal mixing approach (NMA) and two-stage mixing approach (TSMA) by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Four kinds of physio-chemical reactions have been recorded from the concrete samples, including the dehydration of C(3)S(2)H(3), iron-substituted ettringite, dehydroxylation of CH and development of C(6)S(3)H at about 90 degrees C, 135 degrees C, 441 degrees C and 570 degrees C, respectively. From the DSC results, it is confirmed that the concrete samples with RA substitution have generated less amount of strength enhancement chemical products when compared to those without RA substitution. However, the results from the TSMA are found improving the RAC quality. The pre-mix procedure of the TSMA can effectively develop some strength enhancing chemical products including, C(3)S(2)H(3), ettringite, CH and C(6)S(3)H, which shows that RAC made from the TSMA can improve the hydration processes. PMID:18718710

  15. [Recent results in research on oscillatory chemical reactions].

    PubMed

    Poros, Eszter; Kurin-Csörgei, Krisztina

    2014-01-01

    The mechanisms of the complicated periodical phenomenas in the nature (e.g. hearth beat, sleep cycle, circadian rhythms, etc) could be understood with using the laws of nonlinear chemical systems. In this article the newest result in the research of the subfield of nonlinear chemical dynamics aimed at constructing oscillatory chemical reactions, which are novel either in composition or in configuration, are presented. In the introductory part the concept of chemical periodicity is defined, then the forms as it can appear in time and space and the methods of their study are discussed. Detailed description of the experimental work that has resulted in two significant discoveries is provided. A method was developed to design pH-oscillators which are capable of operating under close conditions. The batch pH-oscillators are more convenient to use in some proposed applications than the equivalent CSTR variant. A redox oscillator that is new in composition was found. The permanganate oxidation of some amino acids was shown to take place according to oscillatory kinetics in a narrow range of the experimental parameters. The KMnO4 - glycine - Na2HPO4 system represents the first example in the family of manganese based oscillators where amino acids is involved. In the conclusion formal analogies between the simple chemical and some more complicated biological oscillatory phenomena are mentioned and the possibility of modeling periodic processes with the use of information gained from the studies of chemical oscillations is pointed out. PMID:25872277

  16. Chemical reaction dynamics using the Advanced Light Source

    SciTech Connect

    Yang, X.; Blank, D.A.; Heimann, P.A.; Lee, Y.T.; Suits, A.G. [Univ. of California, Berkeley, CA (US). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (US); Lin, J. [Univ. of California, Berkeley, CA (US). Dept. of Chemistry; Wodtke, A.M. [Univ. of California, Santa Barbara, CA (US). Dept. of Chemistry

    1995-09-01

    The recently commissioned Advanced Light Source (ALS) at Berkeley provides a high brightness, tunable VUV light source for chemical dynamics studies. A dedicated chemical dynamics beamline has been built at the ALS for studies of fundamental chemical processes. High flux (10{sup 16} photon/s with 2% bandwidth) VUV synchrotron radiation from 5 to 30 eV can be obtained from the beamline, whose source is the U8/10 undulator. Three endstations will be in operation for studies ranging from crossed beam reaction dynamics and photodissociation to high resolution photoionization dynamics and spectroscopy. A rotatable source crossed molecular beam apparatus (endstation one) has been established for unimolecular and bimolecular reactive scattering studies. Photodissociation of methylamine and ozone were carried out using VUV synchrotron radiation as the ionization detection technique at this endstation. Results show the advantages of the new endstation using VUV ionization as the detection scheme over similar machines using electron bombardment as the ionization source.

  17. Reversible chemical reactions for single-color multiplexing microscopy.

    PubMed

    Brox, Dominik; Schwering, Michael; Engelhardt, Johann; Herten, Dirk-Peter

    2014-08-01

    Recent developments in biology demand an increasing number of simultaneously imaged structures with standard fluorescence microscopy. However, the number of multiplexed channels is limited for most multiplexing modalities, such as spectral multiplexing or fluorescence-lifetime imaging. We propose extending the number of imaging channels by using chemical reactions, controlling the emissive state of fluorescent dyes. As proof of concept, we reversibly switch a fluorescent copper sensor to enable successive imaging of two different structures in the same spectral channel. We also show that this chemical multiplexing is orthogonal to existing methods. By using two different dyes, we combine chemical with spectral multiplexing for the simultaneous imaging of four different structures with only two spectrally different channels. We characterize and discuss the approach and provide perspectives for extending imaging modalities in stimulated emission depletion microscopy, for which spectral multiplexing is technically demanding. PMID:24753024

  18. Computational Analyses of Complex Flows with Chemical Reactions

    NASA Astrophysics Data System (ADS)

    Bae, Kang-Sik

    The heat and mass transfer phenomena in micro-scale for the mass transfer phenomena on drug in cylindrical matrix system, the simulation of oxygen/drug diffusion in a three dimensional capillary network, and a reduced chemical kinetic modeling of gas turbine combustion for Jet propellant-10 have been studied numerically. For the numerical analysis of the mass transfer phenomena on drug in cylindrical matrix system, the governing equations are derived from the cylindrical matrix systems, Krogh cylinder model, which modeling system is comprised of a capillary to a surrounding cylinder tissue along with the arterial distance to veins. ADI (Alternative Direction Implicit) scheme and Thomas algorithm are applied to solve the nonlinear partial differential equations (PDEs). This study shows that the important factors which have an effect on the drug penetration depth to the tissue are the mass diffusivity and the consumption of relevant species during the time allowed for diffusion to the brain tissue. Also, a computational fluid dynamics (CFD) model has been developed to simulate the blood flow and oxygen/drug diffusion in a three dimensional capillary network, which are satisfied in the physiological range of a typical capillary. A three dimensional geometry has been constructed to replicate the one studied by Secomb et al. (2000), and the computational framework features a non-Newtonian viscosity model for blood, the oxygen transport model including in oxygen-hemoglobin dissociation and wall flux due to tissue absorption, as well as an ability to study the diffusion of drugs and other materials in the capillary streams. Finally, a chemical kinetic mechanism of JP-10 has been compiled and validated for a wide range of combustion regimes, covering pressures of 1atm to 40atm with temperature ranges of 1,200 K--1,700 K, which is being studied as a possible Jet propellant for the Pulse Detonation Engine (PDE) and other high-speed flight applications such as hypersonic missiles. The comprehensive skeletal mechanism consists of 58 species and 315 reactions including in CPD, Benzene formation process by the theory for polycyclic aromatic hydrocarbons (PAH) and soot formation process on the constant volume combustor, premixed flame characteristics.

  19. Compare and contrast the reaction coordinate diagrams for chemical reactions and cytoskeletal force generators

    PubMed Central

    Scholey, Jonathan M.

    2013-01-01

    Reaction coordinate diagrams are used to relate the free energy changes that occur during the progress of chemical processes to the rate and equilibrium constants of the process. Here I briefly review the application of these diagrams to the thermodynamics and kinetics of the generation of force and motion by cytoskeletal motors and polymer ratchets as they mediate intracellular transport, organelle dynamics, cell locomotion, and cell division. To provide a familiar biochemical context for discussing these subcellular force generators, I first review the application of reaction coordinate diagrams to the mechanisms of simple chemical and enzyme-catalyzed reactions. My description of reaction coordinate diagrams of motors and polymer ratchets is simplified relative to the rigorous biophysical treatment found in many of the references that I use and cite, but I hope that the essay provides a valuable qualitative representation of the physical chemical parameters that underlie the generation of force and motility at molecular scales. In any case, I have found that this approach represents a useful interdisciplinary framework for understanding, researching, and teaching the basic molecular mechanisms by which motors contribute to fundamental cell biological processes. PMID:23408787

  20. SHEAR LOCALIZATION AND CHEMICAL REACTION IN HIGH-STRAIN, HIGH-STRAIN-RATE DEFORMATION OF

    E-print Network

    Meyers, Marc A.

    SHEAR LOCALIZATION AND CHEMICAL REACTION IN HIGH-STRAIN, HIGH-STRAIN-RATE DEFORMATION OF Ti regions can initiate chemical reaction inside a reac- tive powder mixture. The shear band spacing was H0-induced chemical reactions in silicide systems have been investigated in recent years. Vreeland and coworkers [7

  1. Log-Domain Circuit Models of Chemical Reactions Soumyajit Mandal and Rahul Sarpeshkar

    E-print Network

    Sarpeshkar, Rahul

    Log-Domain Circuit Models of Chemical Reactions Soumyajit Mandal and Rahul Sarpeshkar Department to networks of chemical reactions. Our circuits can be used for transient and steady-state simulations the energy barrier of a chemical reaction, exponentially changing its speed. In an analogous fashion, gate

  2. A Petri Net Approach to Persistence Analysis in Chemical Reaction Networks

    E-print Network

    Sontag, Eduardo

    A Petri Net Approach to Persistence Analysis in Chemical Reaction Networks David Angeli, Patrick De not approach the boundary of this orthant. For chemical reaction networks and other models in biology as well as sufficient conditions for persistence of chemical species in reaction networks

  3. Computational analysis of an instantaneous chemical reaction in a T-microreactor

    E-print Network

    Bothe, Dieter

    Computational analysis of an instantaneous chemical reaction in a T-microreactor Dieter Bothe 1 in liquid systems with very fast irreversible chemical reaction to the case of unequal diffusivities and energy transport. Hence, they are well suited for fast chemical reactions which are seriously affected

  4. Modeling Chemical Reactions with Single Reactant Specie Abhyudai Singh and Jo~ao Pedro Hespanha

    E-print Network

    Hespanha, João Pedro

    Modeling Chemical Reactions with Single Reactant Specie Abhyudai Singh and Jo~ao Pedro Hespanha Abstract-- A procedure for constructing approximate stochastic models for chemical reactions involving involved in a chemical reaction as the continuous state of a polynomial Stochastic Hybrid System (p

  5. Memory Switches in Chemical Reaction Space Naren Ramakrishnan1,2

    E-print Network

    Ramakrishnan, Naren

    Memory Switches in Chemical Reaction Space Naren Ramakrishnan1,2 , Upinder S. Bhalla3 * 1 and family relationships among such switches. We performed a systematic exploration of chemical reaction of bistable systems. Thus, our systematic exploration of chemical reaction space has produced a valuable

  6. Femtosecond Chemically Activated Reactions: Concept of Nonstatistical Activation at High Thermal Energies

    E-print Network

    Kim, Sang Kyu

    Femtosecond Chemically Activated Reactions: Concept of Nonstatistical Activation at High Thermal Femtosecond chemical activation of reactions at very high thermal energies, much above the bond energy of reactions have been central to chemical kinetics and dynamics. Ideally, with lasers, one wishes to deposit

  7. Predicting the Progress of Diffusively Limited Chemical Reactions in the Presence of Chaotic Advection

    E-print Network

    Gollub, Jerry P.

    Predicting the Progress of Diffusively Limited Chemical Reactions in the Presence of Chaotic chemical reactions in two-dimensional fluid flows are investigated using experimentally measured stretchingRevLett.96.024501 PACS numbers: 47.52.+j, 05.45.ÿa, 47.70.Fw, 82.40.Ck Chemical reactions in solution

  8. CHEMICAL REACTIONS AS -LIMIT OF DIFFUSION MARK A. PELETIER, GIUSEPPE SAVARE, AND MARCO VENERONI

    E-print Network

    Veneroni, Marco

    CHEMICAL REACTIONS AS -LIMIT OF DIFFUSION MARK A. PELETIER, GIUSEPPE SAVAR´E, AND MARCO VENERONI a rigorous proof of Kramers's formal derivation, and we show how chemical reactions and diffusion processes can be embedded in a common framework. This allows one to derive a chemical reaction as a singular

  9. STRAIN-INDUCED STRUCTURAL CHANGES AND CHEMICAL REACTIONSII. MODELLING OF REACTIONS

    E-print Network

    Meyers, Marc A.

    STRAIN-INDUCED STRUCTURAL CHANGES AND CHEMICAL REACTIONSÐII. MODELLING OF REACTIONS IN SHEAR BAND V 1997; accepted in revised form 26 April 1998) AbstractÐThe problem on strain-induced chemical reaction is connected with the additional heating due to RIP. A kinetic criterion of chemical reaction is formulated

  10. DNS of a Mach 4 Boundary Layer with Chemical Reactions M. Pino Martin

    E-print Network

    Martín, Pino

    DNS of a Mach 4 Boundary Layer with Chemical Reactions M. Pino Mart´in Graham V. Candler Aerospace understanding of the interaction between turbulent motion and chemical reactions in hypersonic flows is limited to perform a fundamental study of isotropic turbulence interacting with finite-rate chemical reactions

  11. Explicit Collision Simulation of Chemical Reactions in a Graph Based Artifical Chemistry

    E-print Network

    Stadler, Peter F.

    Explicit Collision Simulation of Chemical Reactions in a Graph Based Artifical Chemistry Gil Benk¨uckel Theory method. Here we describe an extension of the model that models chemical reactions as the result, the reactions are simulated in a way that treats the formation and breakage of individual chemical bonds

  12. Boundary Effects on Chaotic Advection-Diffusion Chemical Reactions M. Chertkov1

    E-print Network

    Lebedev, Vladimir

    Boundary Effects on Chaotic Advection-Diffusion Chemical Reactions M. Chertkov1 and V. Lebedev1,2 1 chemical reaction, A B ! C, in a statistically stationary bounded chaotic flow at large Peclet number Pe advection should essentially accelerate chemical reactions rate in fluid phase, since it should lead

  13. A Petri Net Approach to Persistence Analysis in Chemical Reaction Networks

    E-print Network

    De Leenheer, Patrick

    A Petri Net Approach to Persistence Analysis in Chemical Reaction Networks David Angeli, Patrick De not approach the boundary of this orthant. For chemical reaction networks and other models in biology as well as sufficient conditions for of chemical species in reaction networks, and the applicability

  14. HOW TO AVOID OVERCOOKING: OPTIMAL YIELD OF B FROM THE CONSECUTIVE CHEMICAL REACTIONS ABC

    E-print Network

    Salamon, Peter

    HOW TO AVOID OVERCOOKING: OPTIMAL YIELD OF B FROM THE CONSECUTIVE CHEMICAL REACTIONS A´B´C Thor A the consecutive chemical reactions A´B´C both numerically and analytically using temperature as the control. Keywords: Optimal control, Chemical reactions, Temperature control, Optimal yield INTRODUCTION Already half

  15. Molecular dynamics simulations of a chemical reaction; conditions for local equilibrium in a temperature gradient

    E-print Network

    Kjelstrup, Signe

    Molecular dynamics simulations of a chemical reaction; conditions for local equilibrium have examined a simple chemical reaction in a temperature gradient; 2F $ F2. A mechanical model molecular dynamics simulations showed that the chemical reaction is in local thermodynamic as well

  16. On persistence of chemical reaction networks with time-dependent kinetics and no global conservation laws

    E-print Network

    Sontag, Eduardo

    On persistence of chemical reaction networks with time-dependent kinetics and no global for persistence of chemical reaction networks are proposed, which extend those obtained by the authors in previous. Interpreted for chemical reactions and population models, this translates into a "non-extinction property

  17. Multiple equilibria in complex chemical reaction networks: extensions to entrapped species models

    E-print Network

    Craciun, Gheorghe

    Multiple equilibria in complex chemical reaction networks: extensions to entrapped species models G of complex chemical reaction networks, taken with mass-action kinetics, to admit multiple equilibria.) In both papers, it was understood that the reactions were taking place in the context of what chemical

  18. Chemical reactions between cold trapped Ba+ ions and neutral molecules in the gas phase

    E-print Network

    Schiller, Stephan

    Chemical reactions between cold trapped Ba+ ions and neutral molecules in the gas phase B. Roth, D-cooled ion trapping apparatus, we have investigated laser-induced chemical reactions between cold trapped Ba is to investigate chemical reactions between cold atomic and molecular ions trapped in radio-frequency traps

  19. Effect of chemical reactions on decaying isotropic turbulence M. Pino Martin and Graham V. Candler

    E-print Network

    Martín, Pino

    Effect of chemical reactions on decaying isotropic turbulence M. Pino Marti´n and Graham V. Candler combustion flows, however the interaction between turbulent motion and the chemical reactions that occur. In hypersonic flows the dominant chemical reactions are the dissociation and recombination of nitrogen

  20. Single-molecule chemical reactions: Reexamination of the Kramers approach G. Margolin1

    E-print Network

    Barkai, Eli

    Single-molecule chemical reactions: Reexamination of the Kramers approach G. Margolin1 and E; published 2 August 2005 Single-molecule chemical reactions yield insight into fluctuation phenomena.1103/PhysRevE.72.025101 PACS number s : 02.50. r, 82.37.Np, 05.40. a Chemical reaction of a single molecule

  1. WATER RESOURCES RESEARCH, VOL. ???, XXXX, DOI:10.1029/, Simulation of chemical reaction via particle tracking

    E-print Network

    WATER RESOURCES RESEARCH, VOL. ???, XXXX, DOI:10.1029/, Simulation of chemical reaction via Abstract. Chemical reactions may be simulated without regard to local concentrations by ap- plying simple. Introduction Chemical reactions are commonly idealized as an interac- tion between fluids with certain

  2. A general method for the computation of probabilities in systems of first order chemical reactions

    E-print Network

    Djuriæ, Petar M.

    A general method for the computation of probabilities in systems of first order chemical reactions for the computation of molecular population distributions in a system of first-order chemical reactions. The method to model the chemical reactions in a stochastic way rather than with the traditional differential equations

  3. in Press, Physical Review Letters Predicting the progress of diffusively limited chemical reactions

    E-print Network

    Gollub, Jerry P.

    in Press, Physical Review Letters Predicting the progress of diffusively limited chemical reactions: December 9, 2005) The effects of chaotic advection and diffusion on fast chemical reactions in two, fast chemical reactions, numeri- cal studies have attempted to relate product concentra- tion growth

  4. Explicit Collision Simulation of Chemical Reactions in a Graph Based Artifical Chemistry

    E-print Network

    Stadler, Peter F.

    Explicit Collision Simulation of Chemical Reactions in a Graph Based Artifical Chemistry Gil BenkË?uckel Theory method. Here we describe an extension of the model that models chemical reactions as the result, the reactions are simulated in a way that treats the formation and breakage of individual chemical bonds

  5. Toward Accurate Potentials for Condensed-Phase Chemical Reactions: Electrostatically Embedded Multi-Configuration Molecular Mechanics

    E-print Network

    Truhlar, Donald G

    Toward Accurate Potentials for Condensed-Phase Chemical Reactions: Electrostatically Embedded Multi and molecular mechanical (QM/MM) methods have provided powerful means for studying chemical reactions be used in QM/MM methods. The result is a key step toward studying chemical reactions in condensed phases

  6. SENSITIVITY OF CHEMICAL REACTION NETWORKS: A STRUCTURALAPPROACH. 1. EXAMPLES AND THE CARBON METABOLIC NETWORK

    E-print Network

    Fiedler, Bernold

    -1- SENSITIVITY OF CHEMICAL REACTION NETWORKS: A STRUCTURALAPPROACH. 1. EXAMPLES AND THE CARBON of Theoretical Biology, June 21, 2014) #12;-2- Abstract In biological cells, chemical reaction pathways lead information on the network alone. We investigate how the sensitivity responses of chemicals in a reaction

  7. Explicit Collision Simulation of Chemical Reactions in a Graph Based Artificial Chemistry

    E-print Network

    Flamm, Christoph

    Explicit Collision Simulation of Chemical Reactions in a Graph Based Artificial Chemistry Gil Benk¨uckel Theory method. Here we describe an extension of the model that models chemical reactions as the result, the reactions are simulated in a way that treats the formation and breakage of individual chemical bonds

  8. A bisimulation approach to verification of molecular implementations of formal chemical reaction networks

    E-print Network

    Winfree, Erik

    A bisimulation approach to verification of molecular implementations of formal chemical reaction implementations of formal chemical reaction networks by Qing Dong Master of Science in Computer Science Stony Brook University 2012 In molecular computing, chemical reaction networks have been proposed as a high

  9. Explicit Collision Simulation of Chemical Reactions in a Graph Based Artificial Chemistry

    E-print Network

    Flamm, Christoph

    Explicit Collision Simulation of Chemical Reactions in a Graph Based Artificial Chemistry Gil BenkË?uckel Theory method. Here we describe an extension of the model that models chemical reactions as the result, the reactions are simulated in a way that treats the formation and breakage of individual chemical bonds

  10. Chemical reaction rates using the semiclassical Van Vleck initial value representation

    E-print Network

    Miller, William H.

    Chemical reaction rates using the semiclassical Van Vleck initial value representation Charulatha gas phase H+CH4 reaction to a model for a chemical reaction in a polar solvent.15 However, as any, California 94720; and Chemical Sciences Division, Lawrence Berkeley National Laboratory, University

  11. Building robust chemical reaction mechanisms : next generation of automatic model construction software

    E-print Network

    Song, Jing, 1972-

    2004-01-01

    Building proper reaction mechanisms is crucial to model the system dynamic properties for many industrial processes with complex chemical reaction phenomena. Because of the complexity of a reaction mechanism, computer-aided ...

  12. [Anaphylactic reactions to low-molecular weight chemicals].

    PubMed

    Nowak, Daria; Panaszek, Bernard

    2015-01-01

    Low-molecular weight chemicals (haptens) include a large group of chemical compounds occurring in work environment, items of everyday use (cleaning products, clothing, footwear, gloves, furniture), jewelry (earrings, bracelets), drugs, especially in cosmetics. They cause type IV hypersensitive reactions. During the induction phase of delayed-type hypersensitivity, haptens form complexes with skin proteins. After internalization through antigen presenting cells, they are bound to MHC class II molecules. Next, they are exposed against specific T-lymphocytes, what triggers activation of Th1 cells mainly. After repeating exposition to that hapten, during effector phase, Th1 induce production of cytokines affecting non-specific inflammatory cells. Usually, it causes contact dermatitis. However, occasionally incidence of immediate generalized reactions after contact with some kinds of haptens is noticed. A question arises, how the hapten does induce symptoms which are typical for anaphylaxis, and what contributes to amplification of this mechanism. It seems that this phenomenon arises from pathomechanism occurring in contact urticaria syndrome in which an anaphylactic reaction may be caused either by contact of sensitized skin with protein antigens, high-molecular weight allergens, or haptens. One of the hypotheses indicates the leading role of basophiles in this process. Their contact with haptens, may cause to release mediators of immediate allergic reaction (histamine, eicosanoids) and to produce cytokines corresponding to Th2 cells profile. Furthermore, Th17 lymphocytes secreting pro-inflammatory interleukin-17 might be engaged into amplifying hypersensitivity into immediate reactions and regulatory T-cells may play role in the process, due to insufficient control of the activity of effector cells. PMID:25661919

  13. Surface Reaction Kinetics of Ga 1x In x P Growth During Pulsed Chemical Beam Epitaxy

    E-print Network

    Surface Reaction Kinetics of Ga 1­x In x P Growth During Pulsed Chemical Beam Epitaxy N. Dietz 1 growth has been a slow process because little is known about chemical reaction properties and reaction into the surface reaction kinetics during an organometallic deposition process. These insights will allow us

  14. Quantitative global studies of reactomes and metabolomes using a vectorial representation of reactions and chemical compounds

    PubMed Central

    2010-01-01

    Background Global studies of the protein repertories of organisms are providing important information on the characteristics of the protein space. Many of these studies entail classification of the protein repertory on the basis of structure and/or sequence similarities. The situation is different for metabolism. Because there is no good way of measuring similarities between chemical reactions, there is a barrier to the development of global classifications of "metabolic space" and subsequent studies comparable to those done for protein sequences and structures. Results In this work, we propose a vectorial representation of chemical reactions, which allows them to be compared and classified. In this representation, chemical compounds, reactions and pathways may be represented in the same vectorial space. We show that the representation of chemical compounds reflects their physicochemical properties and can be used for predictive purposes. We use the vectorial representations of reactions to perform a global classification of the reactome of the model organism E. coli. Conclusions We show that this unsupervised clustering results in groups of enzymes more coherent in biological terms than equivalent groupings obtained from the EC hierarchy. This hierarchical clustering produces an optimal set of 21 groups which we analyzed for their biological meaning. PMID:20406431

  15. Holistic Metrics for Assessment of the Greenness of Chemical Reactions in the Context of Chemical Education

    ERIC Educational Resources Information Center

    Ribeiro, M. Gabriela T. C.; Machado, Adelio A. S. C.

    2013-01-01

    Two new semiquantitative green chemistry metrics, the green circle and the green matrix, have been developed for quick assessment of the greenness of a chemical reaction or process, even without performing the experiment from a protocol if enough detail is provided in it. The evaluation is based on the 12 principles of green chemistry. The…

  16. Assessment of existing H2/O2 chemical reaction mechanisms at reheat gas turbine conditions

    E-print Network

    Weydahl, Torleif; Seljeskog, Morten; Haugen, Nils Erland L

    2011-01-01

    This paper provides detailed comparisons of chemical reaction mechanisms of H2 applicable at high preheat temperatures and pressures relevant to gas turbine and particularly Alstom's reheat gas turbine conditions. It is shown that the available reaction mechanisms exhibit large differences in several important elementary reaction coefficients. The reaction mechanisms are assessed by comparing ignition delay and laminar flame speed results obtained from CHEMKIN with available data, however, the amount of data at these conditions is scarce and a recommended candidate among the mechanisms can presently not be selected. Generally, the results with the GRI-Mech and Leeds mechanisms deviate from the Davis, Li, O'Conaire, Konnov and San Diego mechanisms, but there are also significant deviations between the latter five mechanisms that altogether are better adapted to hydrogen. The differences in ignition delay times between the dedicated hydrogen mechanisms (O'Conaire, Li and Konnov) range from approximately a maxim...

  17. Kinetics and thermodynamics of chemical reactions in Li/SOCl2 cells

    NASA Technical Reports Server (NTRS)

    Hansen, Lee D.; Frank, Harvey

    1987-01-01

    Work is described that was designed to determine the kinetic constants necessary to extrapolate kinetic data on Li/SOCl2 cells over the temperature range from 25 to 75 C. A second objective was to characterize as far as possible the chemical reactions that occur in the cells since these reactions may be important in understanding the potential hazards of these cells. The kinetics of the corrosion processes in undischarged Li/SOCl2 cells were determined and separated according to their occurrence at the anode and cathode; the effects that switching the current on and off has on the corrosion reactions was determined; and the effects of discharge state on the kinetics of the corrosion process were found. A thermodynamic analysis of the current-producing reactions in the cell was done and is included.

  18. Review and analysis of high temperature chemical reactions and the effect of non-equilibrium conditions

    NASA Technical Reports Server (NTRS)

    Johnson, R. E.

    1986-01-01

    Chemical reactions at high temperatures have been considered extensively because of their importance to the heating effects on re-entry of space vehicles. Data on these reactions however, are not abundant and even when found there are discrepancies in data collected by various investigators. In particular, data for recombination reactions are calculated from the dissociation reactions or vice versa through the equilibrium constant. This involves the use of the principle of detailed balancing. This principle is discussed in reference to conditions where it is valid as well as to those where it is not valid. Related topics that merit further study or for which applicable information was available are briefly mentioned in an appendix to this report.

  19. Computational organic chemistry: bridging theory and experiment in establishing the mechanisms of chemical reactions.

    PubMed

    Cheng, Gui-Juan; Zhang, Xinhao; Chung, Lung Wa; Xu, Liping; Wu, Yun-Dong

    2015-02-11

    Understanding the mechanisms of chemical reactions, especially catalysis, has been an important and active area of computational organic chemistry, and close collaborations between experimentalists and theorists represent a growing trend. This Perspective provides examples of such productive collaborations. The understanding of various reaction mechanisms and the insight gained from these studies are emphasized. The applications of various experimental techniques in elucidation of reaction details as well as the development of various computational techniques to meet the demand of emerging synthetic methods, e.g., C-H activation, organocatalysis, and single electron transfer, are presented along with some conventional developments of mechanistic aspects. Examples of applications are selected to demonstrate the advantages and limitations of these techniques. Some challenges in the mechanistic studies and predictions of reactions are also analyzed. PMID:25568962

  20. Computed Potential Energy Surfaces and Minimum Energy Pathway for Chemical Reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Langhoff, S. R. (Technical Monitor)

    1994-01-01

    Computed potential energy surfaces are often required for computation of such observables as rate constants as a function of temperature, product branching ratios, and other detailed properties. We have found that computation of the stationary points/reaction pathways using CASSCF/derivative methods, followed by use of the internally contracted CI method with the Dunning correlation consistent basis sets to obtain accurate energetics, gives useful results for a number of chemically important systems. Applications to complex reactions leading to NO and soot formation in hydrocarbon combustion are discussed.

  1. Chemical reactions of mercury in combustion flue gases

    Microsoft Academic Search

    B. Hall; P. Schager; O. Lindqvist

    1991-01-01

    Atmospheric Hg is present in different physical and chemical forms, which determine its atmospheric transformation and transport\\u000a capacities. The chemistry of Hg in flue gases is thus of importance for the deposition pattern around point source emissions.\\u000a In order to apply Hg cleaning methods in flue gases its speciation is also of importance. To investigate this under realistic\\u000a conditions, a

  2. Chemical reaction rates and non-equilibrium pressure of reacting gas mixtures in the state-to-state approach

    NASA Astrophysics Data System (ADS)

    Kustova, Elena V.; Kremer, Gilberto M.

    2014-12-01

    Viscous gas flows with vibrational relaxation and chemical reactions in the state-to-state approach are analyzed. A modified Chapman-Enskog method is used for the determination of chemical reaction and vibrational transition rates and non-equilibrium pressure. Constitutive equations depend on the thermodynamic forces: velocity divergence and chemical reaction/transition affinity. As an application, N2 flow with vibrational relaxation across a shock wave is investigated. Two distinct processes occur behind the shock: for small values of the distance the affinity is large and vibrational relaxation is in its initial stage; for large distances the affinity is small and the chemical reaction is in its final stage. The affinity contributes more to the transition rate than the velocity divergence and the effect of these two contributions are more important for small distances from the shock front. For the non-equilibrium pressure, the term associated with the bulk viscosity increases by a small amount the hydrostatic pressure.

  3. Chemical Nature and Reaction Mechanisms of the Molybdenum Cofactor of Xanthine Oxidoreductase

    PubMed Central

    Okamoto, Ken; Kusano, Teruo; Nishino, Takeshi

    2013-01-01

    Xanthine oxidoreductase (XOR), a complex flavoprotein, catalyzes the metabolic reactions leading from hypoxanthine to xanthine and from xanthine to urate, and both reactions take place at the molybdenum cofactor. The enzyme is a target of drugs for therapy of gout or hyperuricemia. We review the chemical nature and reaction mechanisms of the molybdenum cofactor of XOR, focusing on molybdenum-dependent reactions of actual or potential medical importance, including nitric oxide (NO) synthesis. It is now generally accepted that XOR transfers the water-exchangeable -OH ligand of the molybdenum atom to the substrate. The hydroxyl group at OH-Mo(IV) can be replaced by urate, oxipurinol and FYX-051 derivatives and the structures of these complexes have been determined by x-ray crystallography under anaerobic conditions. Although formation of NO from nitrite or formation of xanthine from urate by XOR is chemically feasible, it is not yet clear whether these reactions have any physiological significance since the reactions are catalyzed at a slow rate even under anaerobic conditions. PMID:23116398

  4. Isothermal Reactor for Continuous Flow Microwave-Assisted Chemical Reaction

    NASA Astrophysics Data System (ADS)

    Matsuzawa, Mitsuhiro; Togashi, Shigenori; Hasebe, Shinji

    An isothermal reactor in which reaction solutions can be controlled at constant temperature under constant microwave irradiation was developed. This is useful for investigating microwave effects on chemical reactions that are not observed under conventional heating conditions. We devised a structure in which a heat-transfer medium with a low dielectric loss factor, which hardly absorbs any microwaves, flowed outside a spiral reaction tube and designed the basic structure of the reactor using electromagnetic simulation to optimize the energy absorption rate. The conditions for increasing the temperature controlling ability of the reactor were also investigated theoretically and experimentally by taking into consideration the influences of three elements: the velocity of the internal fluid, the material for the tube, and the velocity of the external fluid. The velocity of the external fluid had the greatest influence on temperature controlling ability and the material for the tube had the least influence under the experimental conditions. The overall heat transfer coefficient was about 3.9×102 W/(m2·K) when water flowed through the quartz reaction tube at 7.1 mm/s and the external fluid flowed outside the tube at 44 mm/s. We also tested and confirmed that the temperature of water used as internal fluid could be controlled to within ±1.5 K at 309.3 K when microwaves at 26 W were irradiated into the reactor, whereas the temperature of water was over 373 K and boiled without the heat-transfer medium flowing outside the reaction tube using a conventional method of microwave heating. In addition, we investigated microwave effects on Suzuki-Miyaura coupling reaction using the developed isothermal reactor and we confirmed that the temperatures were controlled well in the reactor. The yields obtained by microwave heating were almost the same as that obtained by oil-bath heating.

  5. Solving the chemical master equation for monomolecular reaction systems analytically.

    PubMed

    Jahnke, Tobias; Huisinga, Wilhelm

    2007-01-01

    The stochastic dynamics of a well-stirred mixture of molecular species interacting through different biochemical reactions can be accurately modelled by the chemical master equation (CME). Research in the biology and scientific computing community has concentrated mostly on the development of numerical techniques to approximate the solution of the CME via many realizations of the associated Markov jump process. The domain of exact and/or efficient methods for directly solving the CME is still widely open, which is due to its large dimension that grows exponentially with the number of molecular species involved. In this article, we present an exact solution formula of the CME for arbitrary initial conditions in the case where the underlying system is governed by monomolecular reactions. The solution can be expressed in terms of the convolution of multinomial and product Poisson distributions with time-dependent parameters evolving according to the traditional reaction-rate equations. This very structured representation allows to deduce easily many properties of the solution. The model class includes many interesting examples. For more complex reaction systems, our results can be seen as a first step towards the construction of new numerical integrators, because solutions to the monomolecular case provide promising ansatz functions for Galerkin-type methods. PMID:16953443

  6. An Overview of Chemical Processes That Damage Cellular DNA: Spontaneous Hydrolysis, Alkylation, and Reactions with Radicals

    PubMed Central

    Gates, Kent S.

    2009-01-01

    The sequence of heterocyclic bases on the interior of the DNA double helix constitutes the genetic code that drives the operation of all living organisms. With this said, it is not surprising that chemical modification of cellular DNA can have profound biological consequences. Therefore, the organic chemistry of DNA damage is fundamentally important to diverse fields including medicinal chemistry, toxicology, and biotechnology. This review is designed to provide a brief overview of the common types of chemical reactions that lead to DNA damage under physiological conditions. PMID:19757819

  7. Thermal energy storage. [by means of chemical reactions

    NASA Technical Reports Server (NTRS)

    Grodzka, P. G.

    1975-01-01

    The principles involved in thermal energy storage by sensible heat, chemical potential energy, and latent heat of fusion are examined for the purpose of evolving selection criteria for material candidates in the low ( 0 C) and high ( 100 C) temperature ranges. The examination identifies some unresolved theoretical considerations and permits a preliminary formulation of an energy storage theory. A number of candidates in the low and high temperature ranges are presented along with a rating of candidates or potential candidates. A few interesting candidates in the 0 to 100 C region are also included. It is concluded that storage by means of reactions whose reversibility can be controlled either by product removal or by catalytic means appear to offer appreciable advantages over storage with reactions whose reversability cannot be controlled. Among such advantages are listed higher heat storage capacities and more favorable options regarding temperatures of collection, storage, and delivery. Among the disadvantages are lower storage efficiencies.

  8. A quantum informational approach for dissecting chemical reactions

    NASA Astrophysics Data System (ADS)

    Duperrouzel, Corinne; Tecmer, Pawe?; Boguslawski, Katharina; Barcza, Gergely; Legeza, Örs; Ayers, Paul W.

    2015-02-01

    We present a conceptionally different approach to dissect bond-formation processes in metal-driven catalysis using concepts from quantum information theory. Our method uses the entanglement and correlation among molecular orbitals to analyze changes in electronic structure that accompany chemical processes. As a proof-of-principle example, the evolution of nickel-ethene bond-formation is dissected, which allows us to monitor the interplay of back-bonding and ?-donation along the reaction coordinate. Furthermore, the reaction pathway of nickel-ethene complexation is analyzed using quantum chemistry methods, revealing the presence of a transition state. Our study supports the crucial role of metal-to-ligand back-donation in the bond-forming process of nickel-ethene.

  9. Mass Spectroscopy of Chemical Reaction of 3d Metal Clusters Involved in Chemical Vapor Deposition Synthesis of Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Inoue, Shuhei; Maruyama, Shigeo

    2008-04-01

    The chemical reactions of transition metal clusters in the gas phase have aroused considerable scientific interest and are also of critical scientific importance. For example, these reactions are involved in the synthesis of single-walled carbon nanotubes, which are considered ideal materials because of their outstanding properties. Alcohol catalytic chemical vapor deposition (ACCVD) is one of the best synthetic processes for carbon nanotubes (CNTs); however, even the initial growth mechanism is still unclear, unlike those of other synthetic processes. In this study, we used a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer to determine the initial reactions of transition metal cluster ions (iron, cobalt, and nickel) that are typically adopted in the alcohol CVD process. Metal clusters with approximately 10-25 atoms each, generated by a pulsed laser ablation system in a supersonic-expansion cluster beam source, were directly carried into the FT-ICR cell. Subsequently, ethanol was introduced into the ICR cell. We observed two different results: one was simple chemisorption observed in the iron cluster and the other was dehydrogenated chemisorption observed in the nickel cluster; however, cobalt clusters exhibited both patterns, and a sequential reaction was observed. Furthermore, the dehydrogenation of ethanol on the cobalt cluster is fully described from isotope-labeled experiments.

  10. Structural cluster analysis of chemical reactions in solution

    NASA Astrophysics Data System (ADS)

    Gallet, Grégoire A.; Pietrucci, Fabio

    2013-08-01

    We introduce a simple and general approach to the problem of clustering structures from atomic trajectories of chemical reactions in solution. By considering distance metrics which are invariant under permutation of identical atoms or molecules, we demonstrate that it is possible to automatically resolve as distinct structural clusters the configurations corresponding to reactants, products, and transition states, even in presence of atom-exchanges and of hundreds of solvent molecules. Our approach strongly simplifies the analysis of large trajectories and it opens the way to the construction of kinetic network models of activated processes in solution employing the available efficient schemes developed for proteins conformational ensembles.

  11. Method for detecting pollutants. [through chemical reactions and heat treatment

    NASA Technical Reports Server (NTRS)

    Rogowski, R. S.; Richards, R. R.; Conway, E. J. (inventors)

    1976-01-01

    A method is described for detecting and measuring trace amounts of pollutants of the group consisting of ozone, nitrogen dioxide, and carbon monoxide in a gaseous environment. A sample organic solid material that will undergo a chemical reaction with the test pollutant is exposed to the test environment and thereafter, when heated in the temperature range of 100-200 C., undergoes chemiluminescence that is measured and recorded as a function of concentration of the test pollutant. The chemiluminescence of the solid organic material is specific to the pollutant being tested.

  12. Assessment of reaction-rate predictions of a collision-energy approach for chemical reactions in atmospheric flows.

    SciTech Connect

    Gallis, Michail A.; Bond, Ryan Bomar; Torczynski, John Robert

    2010-06-01

    A recently proposed approach for the Direct Simulation Monte Carlo (DSMC) method to calculate chemical-reaction rates is assessed for high-temperature atmospheric species. The new DSMC model reproduces measured equilibrium reaction rates without using any macroscopic reaction-rate information. Since it uses only molecular properties, the new model is inherently able to predict reaction rates for arbitrary non-equilibrium conditions. DSMC non-equilibrium reaction rates are compared to Park's phenomenological nonequilibrium reaction-rate model, the predominant model for hypersonic-flow-field calculations. For near-equilibrium conditions, Park's model is in good agreement with the DSMC-calculated reaction rates. For far-from-equilibrium conditions, corresponding to a typical shock layer, significant differences can be found. The DSMC predictions are also found to be in very good agreement with measured and calculated non-equilibrium reaction rates, offering strong evidence that this is a viable and reliable technique to predict chemical reaction rates.

  13. Anthropogenic reaction parameters--the missing link between chemical intuition and the available chemical space.

    PubMed

    Keser?, György M; Soós, Tibor; Kappe, C Oliver

    2014-08-01

    How do skilled synthetic chemists develop good intuitive expertise? Why can we only access such a small amount of the available chemical space-both in terms of the reactions used and the chemical scaffolds we make? We argue here that these seemingly unrelated questions have a common root and are strongly interdependent. We performed a comprehensive analysis of organic reaction parameters dating back to 1771 and discovered that there are several anthropogenic factors that limit reaction parameters and thus the scope of synthetic chemistry. Nevertheless, many of the anthropogenic limitations such as narrow parameter space and the opportunity for rapid and clear feedback on the progress of reactions appear to be crucial for the acquisition of valid and reliable chemical intuition. In parallel, however, all of these same factors represent limitations for the exploration of available chemistry space and we argue that these are thus at least partly responsible for limited access to new chemistries. We advocate, therefore, that the present anthropogenic boundaries can be expanded by a more conscious exploration of "off-road" chemistry that would also extend the intuitive knowledge of trained chemists. PMID:24877159

  14. Following a chemical reaction using high-harmonic interferometry.

    PubMed

    Wörner, H J; Bertrand, J B; Kartashov, D V; Corkum, P B; Villeneuve, D M

    2010-07-29

    The study of chemical reactions on the molecular (femtosecond) timescale typically uses pump laser pulses to excite molecules and subsequent probe pulses to interrogate them. The ultrashort pump pulse can excite only a small fraction of molecules, and the probe wavelength must be carefully chosen to discriminate between excited and unexcited molecules. The past decade has seen the emergence of new methods that are also aimed at imaging chemical reactions as they occur, based on X-ray diffraction, electron diffraction or laser-induced recollision--with spectral selection not available for any of these new methods. Here we show that in the case of high-harmonic spectroscopy based on recollision, this apparent limitation becomes a major advantage owing to the coherent nature of the attosecond high-harmonic pulse generation. The coherence allows the unexcited molecules to act as local oscillators against which the dynamics are observed, so a transient grating technique can be used to reconstruct the amplitude and phase of emission from the excited molecules. We then extract structural information from the amplitude, which encodes the internuclear separation, by quantum interference at short times and by scattering of the recollision electron at longer times. The phase records the attosecond dynamics of the electrons, giving access to the evolving ionization potentials and the electronic structure of the transient molecule. In our experiment, we are able to document a temporal shift of the high-harmonic field of less than an attosecond (1 as = 10(-18) s) between the stretched and compressed geometry of weakly vibrationally excited Br(2) in the electronic ground state. The ability to probe structural and electronic features, combined with high time resolution, make high-harmonic spectroscopy ideally suited to measuring coupled electronic and nuclear dynamics occurring in photochemical reactions and to characterizing the electronic structure of transition states. PMID:20671706

  15. Coupling of hydrologic transport and chemical reactions in a stream affected by acid mine drainage

    USGS Publications Warehouse

    Kimball, B.A.; Broshears, R.E.; Bencala, K.E.; McKnight, D.M.

    1994-01-01

    Experiments in St. Kevin Gulch, an acid mine drainage stream, examined the coupling of hydrologic transport to chemical reactions affecting metal concentrations. Injection of LiCl as a conservative tracer was used to determine discharge and residence time along a 1497-m reach. Transport of metals downstream from inflows of acidic, metal-rich water was evaluated based on synoptic samples of metal concentrations and the hydrologic characteristics of the stream. Transport of SO4 and Mn was generally conservative, but in the subreaches most affected by acidic inflows, transport was reactive. Both 0.1-??m filtered and particulate Fe were reactive over most of the stream reach. Filtered Al partitioned to the particulate phase in response to high instream concentrations. Simulations that accounted for the removal of SO4, Mn, Fe, and Al with first-order reactions reproduced the steady-state profiles. The calculated rate constants for net removal used in the simulations embody several processes that occur on a stream-reach scale. The comparison between rates of hydrologie transport and chemical reactions indicates that reactions are only important over short distances in the stream near the acidic inflows, where reactions occur on a comparable time scale with hydrologic transport and thus affect metal concentrations.

  16. Solar-chemical energy conversion via reversible liquid phase Diels-Alder reactions. Final technical report

    SciTech Connect

    Lenz, T.G.; Hegedus, L.S.; Vaughan, J.D.

    1983-05-01

    Thermochemical energy conversion at moderate or low temperature (< about 400/sup 0/C) employing liquid phase components throughout a cycle is suggested as a promising concept for high-efficiency conversion of solar energy to a convenient chemical form. In particular, we propose liquid phase Diels-Alder cycloaddition chemistry as an important class of reversible reactions for such low or moderate temperature thermochemical energy conversion systems. One of the important attributes of thermally driven Diels-Alder reactions is their concerted mechanism, with consequent high yields and efficiencies relative to liquid photochemical systems. Since the systems we propose involve organic species, with thermal stability concerns about 400/sup 0/C, it is important to demonstrate equilibrium shift capability for the highly energetic reactions sought. We have therefore carried out experimental studies with model liquid Diels-Alder systems that clearly demonstrate the degree of control over equilibrium available through substituent entropy effects. These results are of importance as regards subsequent systematic identification of Diels-Alder reactions having ideal thermochemical and physical properties.

  17. The quantum dynamics of electronically nonadiabatic chemical reactions

    NASA Technical Reports Server (NTRS)

    Truhlar, Donald G.

    1993-01-01

    Considerable progress was achieved on the quantum mechanical treatment of electronically nonadiabatic collisions involving energy transfer and chemical reaction in the collision of an electronically excited atom with a molecule. In the first step, a new diabatic representation for the coupled potential energy surfaces was created. A two-state diabatic representation was developed which was designed to realistically reproduce the two lowest adiabatic states of the valence bond model and also to have the following three desirable features: (1) it is more economical to evaluate; (2) it is more portable; and (3) all spline fits are replaced by analytic functions. The new representation consists of a set of two coupled diabatic potential energy surfaces plus a coupling surface. It is suitable for dynamics calculations on both the electronic quenching and reaction processes in collisions of Na(3p2p) with H2. The new two-state representation was obtained by a three-step process from a modified eight-state diatomics-in-molecules (DIM) representation of Blais. The second step required the development of new dynamical methods. A formalism was developed for treating reactions with very general basis functions including electronically excited states. Our formalism is based on the generalized Newton, scattered wave, and outgoing wave variational principles that were used previously for reactive collisions on a single potential energy surface, and it incorporates three new features: (1) the basis functions include electronic degrees of freedom, as required to treat reactions involving electronic excitation and two or more coupled potential energy surfaces; (2) the primitive electronic basis is assumed to be diabatic, and it is not assumed that it diagonalizes the electronic Hamiltonian even asymptotically; and (3) contracted basis functions for vibrational-rotational-orbital degrees of freedom are included in a very general way, similar to previous prescriptions for locally adiabatic functions in various quantum scattering algorithms.

  18. Transport Properties of a Kinetic Model for Chemical Reactions without Barriers

    SciTech Connect

    Alves, Giselle M. [Escola Tecnica, Universidade Federal do Parana, Curitiba (Brazil); Kremer, Gilberto M. [Departamento de Fisica, Universidade Federal do Parana, Curitiba (Brazil); Soares, Ana Jacinta [Departamento de Matematica, Universidade do Minho, Braga (Portugal)

    2011-05-20

    A kinetic model of the Boltzmann equation for chemical reactions without energy barrier is considered here with the aim of evaluating the reaction rate and characterizing the transport coefficient of shear viscosity for the reactive system. The Chapman-Enskog solution of the Boltzmann equation is used to compute the chemical reaction effects, in a flow regime for which the reaction process is close to the final equilibrium state. Some numerical results are provided illustrating that the considered chemical reaction without energy barrier can induce an appreciable influence on the reaction rate and on the transport coefficient of shear viscosity.

  19. A chemical reaction heat pump system adopting the reactive distillation process

    Microsoft Academic Search

    Yonsoo Chung; Seungki Hong; Hyung Keun Song

    1996-01-01

    A new configuration of the chemical reaction heat pump system using 2-propanol dehydrogenation and acetone hydrogenation reactions was proposed in this study. To overcome the intrinsic thermodynamic limitation of chemical reaction heat pump systems, the reactive distillation process was adopted. Through the experimental study, the new configuration showed the better performance compared to previous ones. This study revealed a new

  20. Experimental Re-Examination of the Law of Conservation of Mass in Chemical Reactions

    Microsoft Academic Search

    KLAUS VOLKAMER; CHRISTOPH STREICHER; KENNETH G. WALTON; JOHN FAGAN

    At the beginning of the century the law of conservation of mass in chemical reactions was checked experimentally by Landolt and various other experimenters. Even though in 8 of the 10 chemical reactions studied by Landolt the validity of conservation of mass was confirmed within the margin of experimental errors, in 2 reactions the pre vs. post comparison of the

  1. A modified next reaction method for simulating chemical systems with time dependent propensities and delays

    E-print Network

    Anderson, David F.

    A modified next reaction method for simulating chemical systems with time dependent propensities; publisher error corrected 28 January 2008 Chemical reaction systems with a low to moderate number with methods that produce statistically exact sample paths such as the Gillespie algorithm or the next reaction

  2. Progression in High School Students' (Aged 16-18) Conceptualizations about Chemical Reactions in Solution.

    ERIC Educational Resources Information Center

    Boo, Hong-Kwen; Watson, J. R.

    2001-01-01

    Explores the development over time of students' understandings of the concept of chemical reaction in the context of two familiar reactions in solution. Based on interviews (n=48), results show that students made some progress in their understanding of the concept of chemical reaction but some fundamental misconceptions remained. (Author/MM)

  3. Reaction ensemble molecular dynamics: Direct simulation of the dynamic equilibrium properties of chemically reacting mixtures

    E-print Network

    Lisal, Martin

    diffusion) as well as reaction equilibria for chemically reacting mixtures. DOI: 10.1103/PhysRevE.70.) on chemical reaction equilibria is critical in many fields of science including mixture separationReaction ensemble molecular dynamics: Direct simulation of the dynamic equilibrium properties

  4. Low-energy electron-stimulated chemical reactions of CO in water ice

    NASA Astrophysics Data System (ADS)

    Yamamoto, S.; Beniya, A.; Mukai, K.; Yamashita, Y.; Yoshinobu, J.

    2004-04-01

    We investigated low-energy electron-stimulated chemical reactions between CO and water molecules in low-temperature ice using infrared reflection absorption spectroscopy. Carbon dioxide, the formyl radical, formaldehyde, and methanol were produced by electron irradiation of the water/CO/water layered ice. The electron energy threshold and temperature dependence for the chemical reactions were investigated to elucidate the reaction mechanisms.

  5. The water-gas shift (WGS) reaction (CO + H2O = CO2+ H2) is an important reaction for hydrogen upgrading during fuel

    E-print Network

    Napp, Nils

    Reports The water-gas shift (WGS) reaction (CO + H2O = CO2+ H2) is an important reaction for the WGS reaction (~45 kJ/mol) for gold (Au) vs. ~75 kJ/mol for platinum (3­5), can be exploited for low- temperature WGS and other reactions (6). Low-temperature activity is important to avoid multiple

  6. Lyapunov functions, stationary distributions, and non-equilibrium potential for chemical reaction networks

    E-print Network

    Anderson, David F.

    Lyapunov functions, stationary distributions, and non-equilibrium potential for chemical reaction the well known Lyapunov function of chemical reaction network theory as a scaling limit of the non-equilibrium Abstract We consider the relationship between stationary distributions for stochastic models of chemical

  7. Non-invasive estimation of dissipation from non-equilibrium fluctuations in chemical reactions

    E-print Network

    Lacoste, David

    Non-invasive estimation of dissipation from non-equilibrium fluctuations in chemical reactions S JOURNAL OF CHEMICAL PHYSICS 139, 124109 (2013) Non-invasive estimation of dissipation from non-equilibrium fluctuations in chemical reactions S. Muy,1 A. Kundu,2 and D. Lacoste1 1 Laboratoire de Physico

  8. Molecular Orbital Studies of Zinc Oxide Chemical Vapor Deposition: Gas-Phase Radical Reactions

    E-print Network

    Schlegel, H. Bernhard

    Molecular Orbital Studies of Zinc Oxide Chemical Vapor Deposition: Gas-Phase Radical Reactions-phase reactions involved in the radical mechanism for zinc oxide chemical vapor deposition have been examined in the radical and closed shell mechanisms for zinc oxide chemical vapor deposition shows that the barrier

  9. The Importance of Chemical Substitutes to Chlorofluorocarbons (CFCs)

    Microsoft Academic Search

    Masaaki Yamabe

    The first cholroflurocarbon (CFC), CFC-12 (dichlorodifluoromethane, CCl2F2), was invented by Thomas Midgley, Jr. and Alfred Henne in 1928 by the fluorination reaction of carbon tetrachloride with\\u000a antimony trifluoride, and immediately after it was identified as a best refrigerant in performance, CFC-12 was commercialized\\u000a in 1930 in Du Pont Company as a nonflammable and nontoxic refrigerant to replace toxic refrigerants such

  10. Waste Heat Recovery from Blast Furnace Slag by Chemical Reactions

    NASA Astrophysics Data System (ADS)

    Qin, Yuelin; Lv, Xuewei; Bai, Chenguang; Qiu, Guibao; Chen, Pan

    2012-08-01

    Blast furnace (BF) slag, which is the main byproduct in the ironmaking process, contains large amounts of sensible heat. To recover the heat, a new waste heat-recovery system—granulating molten BF slag by rotary multinozzles cup atomizer and pyrolyzing printed circuited board with obtained hot BF slag particle—was proposed in this study. The feasibility of the waste heat-recovery system was verified by dry granulation and pyrolyzation experiments. The energy of hot BF slag could be converted to chemical energy through the pyrolysis reaction, and a large amount of combustible gas like CO, H2, C m H n , and CH4 can be generated during the process.

  11. Chemical Reactions in the Processing of Mosi2 + Carbon Compacts

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Lee, Kang N.; Maloy, Stuart A.; Heuer, Arthur H.

    1993-01-01

    Hot-pressing of MoSi2 powders with carbon at high temperatures reduces the siliceous grain boundary phase in the resultant compact. The chemical reactions in this process were examined using the Knudsen cell technique. A 2.3 wt pct oxygen MoSi2 powder and a 0.59 wt pct oxygen MoSi2 powder, both with additions of 2 wt pct carbon, were examined. The reduction of the siliceous grain boundary phase was examined at 1350 K and the resultant P(SiO)/P(CO) ratios interpreted in terms of the SiO(g) and CO(g) isobars on the Si-C-O predominance diagram. The MoSi2 + carbon mixtures were then heated at the hot-pressing temperature of 2100 K. Large weight losses were observed and could be correlated with the formation of a low-melting eutectic and the formation and vaporization of SiC.

  12. Numerical solutions of several reflected shock-wave flow fields with nonequilibrium chemical reactions

    NASA Technical Reports Server (NTRS)

    Hanson, R. K.; Presley, L. L.; Williams, E. V.

    1972-01-01

    The method of characteristics for a chemically reacting gas is used in the construction of the time-dependent, one-dimensional flow field resulting from the normal reflection of an incident shock wave at the end wall of a shock tube. Nonequilibrium chemical reactions are allowed behind both the incident and reflected shock waves. All the solutions are evaluated for oxygen, but the results are generally representative of any inviscid, nonconducting, and nonradiating diatomic gas. The solutions clearly show that: (1) both the incident- and reflected-shock chemical relaxation times are important in governing the time to attain steady state thermodynamic properties; and (2) adjacent to the end wall, an excess-entropy layer develops wherein the steady state values of all the thermodynamic variables except pressure differ significantly from their corresponding Rankine-Hugoniot equilibrium values.

  13. No electron left behind: a rule-based expert system to predict chemical reactions and reaction mechanisms

    PubMed Central

    Chen, Jonathan H.; Baldi, Pierre

    2009-01-01

    Predicting the course and major products of arbitrary reactions is a fundamental problem in chemistry, one that chemists must address in a variety of tasks ranging from synthesis design to reaction discovery. Described here is an expert system to predict organic chemical reactions based on a knowledge base of over 1,500 manually composed reaction transformation rules. Novel rule extensions are introduced to enable robust predictions and describe detailed reaction mechanisms at the level of electron flows in elementary reaction steps, ensuring that all reactions are properly balanced and atom-mapped. The core reaction prediction functionalities of this expert system are illustrated with applications including: (1) prediction of detailed reaction mechanisms; (2) computer-based learning in organic chemistry; (3) retro synthetic analysis; and (4) combinatorial library design. Select applications available via http://cdb.ics.uci.edu. PMID:19719121

  14. Enzyme catalysis Enzyme catalysis is the catalysis of chemical reactions by

    E-print Network

    Cavanagh, John

    Enzyme catalysis Enzyme catalysis is the catalysis of chemical reactions by specialized proteins known as enzymes. Catalysis of biochemical reactions in the cell is vital due to the very low reaction rates of the uncatalysed reactions. The mechanism of enzyme catalysis is similar in principle to other

  15. Mathematically Reduced Chemical Reaction Mechanism Using Neural Networks

    SciTech Connect

    Ziaul Huque

    2007-08-31

    This is the final technical report for the project titled 'Mathematically Reduced Chemical Reaction Mechanism Using Neural Networks'. The aim of the project was to develop an efficient chemistry model for combustion simulations. The reduced chemistry model was developed mathematically without the need of having extensive knowledge of the chemistry involved. To aid in the development of the model, Neural Networks (NN) was used via a new network topology known as Non-linear Principal Components Analysis (NPCA). A commonly used Multilayer Perceptron Neural Network (MLP-NN) was modified to implement NPCA-NN. The training rate of NPCA-NN was improved with the GEneralized Regression Neural Network (GRNN) based on kernel smoothing techniques. Kernel smoothing provides a simple way of finding structure in data set without the imposition of a parametric model. The trajectory data of the reaction mechanism was generated based on the optimization techniques of genetic algorithm (GA). The NPCA-NN algorithm was then used for the reduction of Dimethyl Ether (DME) mechanism. DME is a recently discovered fuel made from natural gas, (and other feedstock such as coal, biomass, and urban wastes) which can be used in compression ignition engines as a substitute for diesel. An in-house two-dimensional Computational Fluid Dynamics (CFD) code was developed based on Meshfree technique and time marching solution algorithm. The project also provided valuable research experience to two graduate students.

  16. Progress in an oxygen-carrier reaction kinetics experiment for rotary-bed chemical looping combustion

    E-print Network

    Jester-Weinstein, Jack (Jack L.)

    2013-01-01

    The design process for an experimental platform measuring reaction kinetics in a chemical looping combustion (CLC) process is documented and justified. To enable an experiment designed to characterize the reaction kinetics ...

  17. The Impact of Fluid Deformation on Mixing and Fast Chemical Reaction Along Reaction Fronts in Porous Media

    NASA Astrophysics Data System (ADS)

    Dentz, Marco; Le Borgne, Tanguy; Ginn, Timothy; Nassar, Mohamed; Bennethum, Lynn S.

    2015-04-01

    Fast chemical reactions in heterogeneous flows are controlled by fluid mixing, which perturbs local chemical equilibria and thus triggers chemical reactions. The deformation of material fluid elements in inhomogeneous flow fields leads to solute spreading and increased mixing due to the steepening of concentration gradients on one hand, and the increase of interfacial surface area between chemicals on the other. We present an approach based on a lamellar representation of fluid mixing that links fluid deformation, the distribution of concentration gradiens, and the upscaled reaction rates for fast reversible reactions. The evolution of effective reaction rates are governed by the flow topology, which determines the distribution of local velocity gradients, and the elongation rate of the reaction front. This leads to a significant increase of reaction efficiency, which turns out to be orders of magnitude larger than in homogeneous flow. This lamella based approach allows for the systematic evaluation of the temporal evolution of equilibrium reaction rates in inhomogeneous flows, and establishes a direct link between the reaction efficiency and the spatial characteristics of the underlying flow field as quantified by the deformation of material fluid elements.

  18. Systematic exploration of the mechanism of chemical reactions: the global reaction route mapping (GRRM) strategy using the ADDF and AFIR methods.

    PubMed

    Maeda, Satoshi; Ohno, Koichi; Morokuma, Keiji

    2013-03-21

    Global reaction route mapping (GRRM), a fully-automated search for all important reaction pathways relevant to a given purpose, on the basis of quantum chemical calculations enables systematic elucidation of complex chemical reaction mechanisms. However, GRRM had previously been limited to very simple systems. This is mainly because such calculations are highly demanding even in small systems when a brute-force sampling is considered. Hence, we have developed two independent but complementary methods: anharmonic downward distortion following (ADDF) and artificial force induced reaction (AFIR) methods. ADDF can follow reaction pathways starting from local minima on the potential energy surface (PES) toward transition structures (TSs) and dissociation channels. AFIR can find pathways starting from two or more reactants toward TSs for their associative reactions. In other words, ADDF searches for A ? X type isomerization and A ? X + Y type dissociation pathways, whereas AFIR finds A + B ? X (+ Y) type associative pathways. Both follow special paths called the ADDF path and the AFIR path, and these tend to pass through near TSs of corresponding reaction pathways, giving approximate TSs. Such approximate TSs can easily be re-optimized to corresponding true TSs by standard geometry optimizations. On the basis of these two methods, we have proposed practical strategies of GRRM. The GRRM strategies have been applied to a variety of chemical systems ranging from thermal- and photochemical-reactions in small systems to organometallic- and enzyme-catalysis, on the basis of quantum chemical calculations. In this perspective, we present an overview of the GRRM strategies and some results of applications. Their practical usage for systematic prediction is also discussed. PMID:23389653

  19. Evaluation of reaction mechanism of coal-metal oxide interactions in chemical-looping combustion

    SciTech Connect

    Siriwardane, Ranjani; Richards, George; Poston, James [US Department of Energy, National Energy Technology Laboratory, 3610 Collins Ferry Road, P.O. Box 880, Morgantown, WV 26507-0880 (United States); Tian, Hanjing; Miller, Duane; Simonyi, Thomas [US Department of Energy, National Energy Technology Laboratory, 3610 Collins Ferry Road, P.O. Box 880, Morgantown, WV 26507-0880 (United States); URS, 3610 Collins Ferry Road, Morgantown, WV 26505 (United States)

    2010-11-15

    The knowledge of reaction mechanism is very important in designing reactors for chemical-looping combustion (CLC) of coal. Recent CLC studies have considered the more technically difficult problem of reactions between abundant solid fuels (i.e. coal and waste streams) and solid metal oxides. A definitive reaction mechanism has not been reported for CLC reaction of solid fuels. It has often been assumed that the solid/solid reaction is slow and therefore requires that reactions be conducted at temperatures high enough to gasify the solid fuel, or decompose the metal oxide. In contrast, data presented in this paper demonstrates that solid/solid reactions can be completed at much lower temperatures, with rates that are technically useful as long as adequate fuel/metal oxide contact is achieved. Density functional theory (DFT) simulations as well as experimental techniques such as thermo-gravimetric analysis (TGA), flow reactor studies, in situ X-ray photo electron spectroscopy (XPS), in situ X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to evaluate how the proximal interaction between solid phases proceeds. The data indicate that carbon induces the Cu-O bond breaking process to initiate the combustion of carbon at temperatures significantly lower than the spontaneous decomposition temperature of CuO, and the type of reducing medium in the vicinity of the metal oxide influences the temperature at which the oxygen release from the metal oxide takes place. Surface melting of Cu and wetting of carbon may contribute to the solid-solid contacts necessary for the reaction. (author)

  20. Optomechanical manipulation of chemical reactions on the nanoscale with optofluidic nanotweezers

    NASA Astrophysics Data System (ADS)

    O'Dell, Dakota; Serey, Xavier; Erickson, David

    2014-03-01

    Chemical reactions are often described as a progression along a reaction coordinate. Waveguide evanescent fields generate an electromagnetic force that spans tens of nanometers and have been used previously to trap protein molecules. Applying this force along a reaction coordinate could radically alter the chemical reaction by modifying the activation energy or biasing the reaction towards a specific pathway. Here, we show that the adsorption of proteins onto carbon nanotubes can be controlled with opto-mechanical forces. An analytic model for the reaction was developed, the predictions of which were explored by probing the energy barrier under various experimental conditions.

  1. Direct Monte Carlo simulation of chemical reaction systems: Internal energy transfer and an energy-dependent unimolecular reaction

    E-print Network

    Anderson, James B.

    Direct Monte Carlo simulation of chemical reaction systems: Internal energy transfer and an energy a direct Monte Carlo simulation of an energy-dependent t&molecular reaction system of the type A+ B can be treated by Monte Carlo simulations. One of the most useful methods is Bird's direct simulation

  2. Computed Potential Energy Surfaces and Minimum Energy Pathways for Chemical Reactions

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Langhoff, S. R. (Technical Monitor)

    1994-01-01

    Computed potential energy surfaces are often required for computation of such parameters as rate constants as a function of temperature, product branching ratios, and other detailed properties. For some dynamics methods, global potential energy surfaces are required. In this case, it is necessary to obtain the energy at a complete sampling of all the possible arrangements of the nuclei, which are energetically accessible, and then a fitting function must be obtained to interpolate between the computed points. In other cases, characterization of the stationary points and the reaction pathway connecting them is sufficient. These properties may be readily obtained using analytical derivative methods. We have found that computation of the stationary points/reaction pathways using CASSCF/derivative methods, followed by use of the internally contracted CI method to obtain accurate energetics, gives usefull results for a number of chemically important systems. The talk will focus on a number of applications including global potential energy surfaces, H + O2, H + N2, O(3p) + H2, and reaction pathways for complex reactions, including reactions leading to NO and soot formation in hydrocarbon combustion.

  3. Chemical Reactions and Atomic Removal Dynamics during Gallium Nitride Chemical Mechanical Polishing Process: Quantum Chemical Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Kentaro; Higuchi, Yuji; Ozawa, Nobuki; Kubo, Momoji

    2015-03-01

    The chemical mechanical polishing (CMP) is promising for efficient polishing of the GaN substrate, and it is essential for manufacturing of GaN devices. However, the detailed CMP mechanisms are unclear, and then the design of efficient and precise CMP process is difficult. We performed polishing simulations of a GaN substrate by a SiO2 abrasive grain in a solution including OH radicals in order to reveal effects of OH radicals on the polishing process. The OH radicals in the solution are adsorbed on the GaN surface and occupy the hollow sites on the surface. Then, a surface-adsorbed O atom is generated by the chemical reaction between the surface-adsorbed OH species and a OH radical in the solution. In the friction interface between the GaN substrate and the abrasive grain, the surface-adsorbed O atom is mechanically pushed into the GaN substrate by the abrasive grain. This O atom intrusion induces the dissociation of Ga-N bonds of the GaN substrate. Moreover, volatile N2 molecules and soluble Ga(OH)3 molecules are generated due to the dissociation of Ga-N bonds. Then, we suggested that the GaN CMP process efficiently proceeds by the mechanically induced chemical reactions: a surface-adsorbed O atom is generated and pushed into the GaN bulk by the abrasive grain.

  4. Chemical Kinetic Data Base for Propellant Combustion. II. Reactions Involving CN, NCO, and HNCO

    NASA Astrophysics Data System (ADS)

    Tsang, Wing

    1992-07-01

    This paper contains evaluated chemical kinetic data on single step elementary reactions involving small polyatomic molecules which are of importance in propellant combustion. The work consists of the collection and evaluation of mechanistic and rate information and the use of various methods for the extrapolation and estimation of rate data where information does not exist. The conditions covered range from 500-2500 K and 1017-1022 particles cm-3. The results of the second year's effort add to the existing data base reactions involving CN, NCO, and HNCO with each other and the following species: H, H2, H2O, O, OH, HCHO, CHO, CO, NO, NO2, HNO, HNO2, HCN, and N2O.

  5. Mathematically Reduced Chemical Reaction Mechanism Using Neural Networks

    SciTech Connect

    Nelson Butuk

    2004-12-01

    This is an annual technical report for the work done over the last year (period ending 9/30/2004) on the project titled ''Mathematically Reduced Chemical Reaction Mechanism Using Neural Networks''. The aim of the project is to develop an efficient chemistry model for combustion simulations. The reduced chemistry model will be developed mathematically without the need of having extensive knowledge of the chemistry involved. To aid in the development of the model, Neural Networks (NN) will be used via a new network topology know as Non-linear Principal Components Analysis (NPCA). We report on the development of a procedure to speed up the training of NPCA. The developed procedure is based on the non-parametric statistical technique of kernel smoothing. When this smoothing technique is implemented as a Neural Network, It is know as Generalized Regression Neural Network (GRNN). We present results of implementing GRNN on a test problem. In addition, we present results of an in house developed 2-D CFD code that will be used through out the project period.

  6. PUBLISHED ONLINE: 22 JULY 2012 | DOI: 10.1038/NPHYS2373 Controlling chemical reactions of a single particle

    E-print Network

    Loss, Daniel

    LETTERS PUBLISHED ONLINE: 22 JULY 2012 | DOI: 10.1038/NPHYS2373 Controlling chemical reactions, chemical reactions have been investigated by tuning thermodynamic parameters, such as temperature on chemical reaction rates and branching ratios, and monitor the kinematics of the reaction products

  7. SUPERPOSITION OF DIFFUSION AND CHEMICAL REACTION CONTROLLED LIMITING CURRENTS - APPLICATION TO CO2 CORROSION

    Microsoft Academic Search

    Srdjan Nesic; B. F. M. Pots; John Postlethwaite; Nicolas Thevenot

    It was observed experimentally that a chemical reaction limiting current can be affected by flow. In the present study a new more general expression than the one found in literature was derived for the superposition of the diffusion and chemical reaction controlled limiting currents . It was found that their interaction in the case of CO 2 corrosion is significant

  8. Introducing Stochastic Simulation of Chemical Reactions Using the Gillespie Algorithm and MATLAB: Revisited and Augmented

    ERIC Educational Resources Information Center

    Argoti, A.; Fan, L. T.; Cruz, J.; Chou, S. T.

    2008-01-01

    The stochastic simulation of chemical reactions, specifically, a simple reversible chemical reaction obeying the first-order, i.e., linear, rate law, has been presented by Martinez-Urreaga and his collaborators in this journal. The current contribution is intended to complement and augment their work in two aspects. First, the simple reversible…

  9. Non-meanfield deterministic limits in chemical reaction kinetics R. E. Lee DeVille

    E-print Network

    Van Den Eijnden, Eric

    Non-meanfield deterministic limits in chemical reaction kinetics R. E. Lee DeVille Courant is demonstrated for the kinetic Monte Carlo version of the Schnakenberg reaction where we identified a scaling, and it is at the very heart of the majority of macroscopic models of physical, chemical, and biological systems

  10. Design criteria for extraction with chemical reaction and liquid membrane permeation

    NASA Technical Reports Server (NTRS)

    Bart, H. J.; Bauer, A.; Lorbach, D.; Marr, R.

    1988-01-01

    The design criteria for heterogeneous chemical reactions in liquid/liquid systems formally correspond to those of classical physical extraction. More complex models are presented which describe the material exchange at the individual droplets in an extraction with chemical reaction and in liquid membrane permeation.

  11. Communications Watching photoinduced chemical reactions in solution in real time by

    E-print Network

    Kling, Matthias

    Angewandte Chemie Communications Watching photoinduced chemical reactions in solution in real time.[5,6] Photo- chemical decomposition has almost exclusively been investigated in the nanosecond of the poor time resolution, a complete mechanistic understanding of the elementary reactions of peroxide

  12. Stochastic simulation of chemical reactions with spatial resolution and single molecule detail

    Microsoft Academic Search

    Steven S. Andrews; Dennis Bray

    2004-01-01

    Methods are presented for simulating chemical reaction networks with a spatial resolution that is accurate to nearly the size scale of individual molecules. Using an intuitive picture of chemical reaction systems, each molecule is treated as a point-like particle that diffuses freely in three-dimensional space. When a pair of reactive molecules collide, such as an enzyme and its substrate, a

  13. The effect of chemical reactions of the injected gas on the aerodynamic heating of blunt bodies

    Microsoft Academic Search

    K. Karashima; K. Nakahashi

    1979-01-01

    The effects on aerodynamic heating of chemical reactions of gaseous materials injected into a shock layer flow due to ablation are examined. Assuming ablation of Teflon and equilibrium chemical reactions, a hypersonic flow past a blunt nosed axisymmetric body with surface injection of C2F4 gas is solved numerically using the VSL equations, and a comparison is made with the results

  14. On the dynamics of chemical reactions of negative ions

    E-print Network

    Mikosch, Jochen; Wester, Roland

    2010-01-01

    This review discusses the dynamics of negative ion reactions with neutral molecules in the gas phase. Most anion-molecule reactions proceed via a qualitatively different interaction potential than cationic or neutral reactions. It has been and still is the goal of many experiments to understand these reaction dynamics and the different reaction mechanisms they lead to. We will show how rate coefficients and cross sections for anion-molecule reactions are measured and interpreted to yield information on the underlying dynamics. We will also present more detailed approaches that study either the transient reaction complex or the energy- and angle-resolved scattering of negative ions with neutral molecules. With the help of these different techniques many aspects of anion-molecule reaction dynamics could be unravelled in the last years. However, we are still far from a complete understanding of the complex molecular interplay that is at work during a negative ion reaction.

  15. Comparison of designed and randomly generated catalysts for simple chemical reactions

    PubMed Central

    Kipnis, Yakov; Baker, David

    2012-01-01

    There has been recent success in designing enzymes for simple chemical reactions using a two-step protocol. In the first step, a geometric matching algorithm is used to identify naturally occurring protein scaffolds at which predefined idealized active sites can be realized. In the second step, the residues surrounding the transition state model are optimized to increase transition state binding affinity and to bolster the primary catalytic side chains. To improve the design methodology, we investigated how the set of solutions identified by the design calculations relate to the overall set of solutions for two different chemical reactions. Using a TIM barrel scaffold in which catalytically active Kemp eliminase and retroaldolase designs were obtained previously, we carried out activity screens of random libraries made to be compositionally similar to active designs. A small number of active catalysts were found in screens of 103 variants for each of the two reactions, which differ from the computational designs in that they reuse charged residues already present in the native scaffold. The results suggest that computational design considerably increases the frequency of catalyst generation for active sites involving newly introduced catalytic residues, highlighting the importance of interaction cooperativity in enzyme active sites. PMID:22811380

  16. Simulating chemical reactions in ionic liquids using QM/MM methodology.

    PubMed

    Acevedo, Orlando

    2014-12-18

    The use of ionic liquids as a reaction medium for chemical reactions has dramatically increased in recent years due in large part to the numerous reported advances in catalysis and organic synthesis. In some extreme cases, ionic liquids have been shown to induce mechanistic changes relative to conventional solvents. Despite the large interest in the solvents, a clear understanding of the molecular factors behind their chemical impact is largely unknown. This feature article reviews our efforts developing and applying mixed quantum and molecular mechanical (QM/MM) methodology to elucidate the microscopic details of how these solvents operate to enhance rates and alter mechanisms for industrially and academically important reactions, e.g., Diels-Alder, Kemp eliminations, nucleophilic aromatic substitutions, and ?-eliminations. Explicit solvent representation provided the medium dependence of the activation barriers and atomic-level characterization of the solute-solvent interactions responsible for the experimentally observed "ionic liquid effects". Technical advances are also discussed, including a linear-scaling pairwise electrostatic interaction alternative to Ewald sums, an efficient polynomial fitting method for modeling proton transfers, and the development of a custom ionic liquid OPLS-AA force field. PMID:25329366

  17. High resolution time-of-flight spectrometer for crossed molecular beam study of elementary chemical reactions

    SciTech Connect

    Qiu Minghui; Che Li; Ren Zefeng; Dai Dongxu; Wang Xiuyan; Yang Xueming [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023 (China)

    2005-08-15

    In this article, we describe an apparatus in our laboratory for investigating elementary chemical reactions using the high resolution time-of-flight Rydberg tagging method. In this apparatus, we have adopted a rotating source design so that collision energy can be changed for crossed beam studies of chemical reactions. Preliminary results on the HI photodissociation and the F atom reaction with H{sub 2} are reported here. These results suggest that the experimental apparatus is potentially a powerful tool for investigating state-to-state dynamics of elementary chemical reactions.

  18. Chemical reactions of ultracold alkali dimers in the lowest-energy $^3\\Sigma$ state

    E-print Network

    Tomza, Micha?; Moszynski, Robert; Krems, Roman V

    2013-01-01

    We show that the interaction of polar alkali dimers in the quintet spin state leads to the formation of a deeply bound reaction complex. The reaction complex can decompose adiabatically into homonuclear alkali dimers (for all molecules except KRb) and into alkali trimers (for all molecules). We show that there are no barriers for these chemical reactions. This means that all alkali dimers in the $a^3\\Sigma^+$ state are chemically unstable at ultracold temperature, and the use of an optical lattice to segregate the molecules and suppress losses may be necessary. In addition, we calculate the minimum energy path for the chemical reactions of alkali hydrides. We find that the reaction of two molecules is accelerated by a strong attraction between the alkali atoms, leading to a barrierless process that produces hydrogen atoms with large kinetic energy. We discuss the unique features of the chemical reactions of ultracold alkali dimers in the $a^3\\Sigma^+$ electronic state.

  19. Numerical study of chemical reactions in a surface microdischarge tube with mist flow based on experiment

    NASA Astrophysics Data System (ADS)

    Shibata, T.; Nishiyama, H.

    2014-03-01

    Recently, a water treatment method of spraying solution into a discharge region has been developed and shows high energy efficiency. In this study, a simulation model of a water treatment method using a surface microdischarge (SMD) tube with mist flow is proposed for further understanding the detailed chemical reactions. Our model has three phases (plasma, gas and liquid) and three simulation steps. The carrier gas is humid air including 2% or 3% water vapour. The chemical species diffusion characteristics in the SMD tube and the concentrations in a droplet are clarified in a wide pH interval. The simulation results show that the chemical species generated on the SMD tube inner wall are diffused to the central axis and dissolved into fine droplets. Especially, OH radicals dissolve into droplets a few mm away from the SMD tube wall because of acidification of the droplets. Furthermore, the hydrogen peroxide density, which is the most important indicator of a radical reaction in water, is influenced by the initial solution pH. This pH dependence results from ozone self-decomposition in water.

  20. Diffusion controlled instantaneous chemical reaction in a thin tube containing fine reactant particles

    Microsoft Academic Search

    Anurag Mehra; P. T. Rao; A. K. Suresh

    1997-01-01

    The instantaneous, chemical reaction between a sparingly soluble gaseous species and a liquid-phase reactant is known to occur at a moving reaction plane to which both the reacting species diffuse. This study investigates the motion of such a reaction front, in thin tubes, where the liquid-phase reactant is present as a slurry of sparingly soluble, fine particles. The movement of

  1. A comparison of reversible chemical reactions for solar thermochemical power generation

    E-print Network

    Boyer, Edmond

    453 A comparison of reversible chemical reactions for solar thermochemical power generation O. M storage of the reaction products. A number of reactions have been proposed for solar thermochemical power to be a good choice for first generation solar thermochemical power generation. Revue Phys. Appl. 15 (1980) 453

  2. A coupled chemical burster: The chlorine dioxide-iodide reaction in two flow reactors

    E-print Network

    Epstein, Irving R.

    A coupled chemical burster: The chlorine dioxide-iodide reaction in two flow reactors Miles Dolnika-iodide reaction has been studied in a system consisting of two continuous flow stirred tank reactors (CSTRs triggered, exponentially decreasing stimulation, and alternating mass exchange. The reaction, which exhibits

  3. CHEMICAL REACTION OF SILICON CLUSTER IONS WITH ETHYLENE BY USING FT-ICR MASS SPECTROMETER

    E-print Network

    Maruyama, Shigeo

    CHEMICAL REACTION OF SILICON CLUSTER IONS WITH ETHYLENE BY USING FT-ICR MASS SPECTROMETER Masamichi transform ion cyclotron resonance (FT-ICR) mass spectrometer and monitored during chemisorption reaction with ethylene (C2H4). Through measurements of "time-dependency" of this reaction process, drastic change

  4. State to State Chemistry This research is concerned with the description of chemical reactions, photoprocesses and

    E-print Network

    State to State Chemistry This research is concerned with the description of chemical reactions are interested in are: 1.Reactions of oxygen atoms with polyatomic molecules (hydrocarbons, fluorinated hydrocarbons) We have performed extensive studies of the reaction of atomic oxygen (O(3 P)) with small

  5. STABILITY OF CHEMICAL REACTIONS IN A CSTR WITH DELAYED RECYCLE STREAM

    E-print Network

    Lehman, Brad

    STABILITY OF CHEMICAL REACTIONS IN A CSTR WITH DELAYED RECYCLE STREAM Brad Lehman' Departmentof, and hence the cost of reaction, its use is widespread in industry. For example, recycling is almost always and alcohol of cyclohexene), among many other reactions. Adifficultywithmuchof

  6. Effect of chaotic interfacial stretching on bimolecular chemical reaction in helical-coil reactors

    Microsoft Academic Search

    David R. Sawyers; Mihir Sen; Hsueh-Chia Chang

    1996-01-01

    We investigate the yield of bimolecular chemical reaction between two initially separated reactants in a tubular reactor of different coiling geometries. Laminar and steady flow with high mass Peclet number, Pe, are assumed. Asymptotic approximations for slow reactions are obtained by studying the reaction at a thin interfacial boundary layer. For a straight tube it is found that the area-averaged

  7. On the deduction of chemical reaction pathways from measurements of time series of concentrations

    NASA Astrophysics Data System (ADS)

    Samoilov, Michael; Arkin, Adam; Ross, John

    2001-03-01

    We discuss the deduction of reaction pathways in complex chemical systems from measurements of time series of chemical concentrations of reacting species. First we review a technique called correlation metric construction (CMC) and show the construction of a reaction pathway from measurements on a part of glycolysis. Then we present two new improved methods for the analysis of time series of concentrations, entropy metric construction (EMC), and entropy reduction method (ERM), and illustrate (EMC) with calculations on a model reaction system.

  8. Kinetic models with chemical reactions and nonequilibrium entropy in open systems

    NASA Astrophysics Data System (ADS)

    Aristov, Vladimir; Frolova, Anna; Zabelok, Sergey

    2014-12-01

    Nonuniform relaxation problems are applied to simulate complex non-equilibrium processes with chemical reactions in open systems. The present paper is a continuation of our studies at a new level, in particular, 2D flows are considered. Besides the slow chemical reactions, the so-called fast reactions are studied. A special attention is paid to studying the behavior of non-equilibrium entropy and entropy flux in such complex open systems.

  9. Using Drawing Technology to Assess Students' Visualizations of Chemical Reaction Processes

    NASA Astrophysics Data System (ADS)

    Chang, Hsin-Yi; Quintana, Chris; Krajcik, Joseph

    2014-06-01

    In this study, we investigated how students used a drawing tool to visualize their ideas of chemical reaction processes. We interviewed 30 students using thinking-aloud and retrospective methods and provided them with a drawing tool. We identified four types of connections the students made as they used the tool: drawing on existing knowledge, incorporating dynamic aspects of chemical processes, linking a visualization to the associated chemical phenomenon, and connecting between the visualization and chemistry concepts. We also compared students who were able to create dynamic visualizations with those who only created static visualizations. The results indicated a relationship between students constructing a dynamic view of chemical reaction processes and their understanding of chemical reactions. This study provides insights into the use of visualizations to support instruction and assessment to facilitate students' integrated understanding of chemical reactions.

  10. Multistep One-Pot Reactions Combining Biocatalysts and Chemical Catalysts for Asymmetric Synthesis

    E-print Network

    Zhao, Huimin

    Multistep One-Pot Reactions Combining Biocatalysts and Chemical Catalysts for Asymmetric Synthesis Carl A. Denard, John F. Hartwig,*, and Huimin Zhao*,,§ Department of Chemical and Biomolecular of chemical catalysts. Over the last 20 years, research in this area has provided us with proof of concept

  11. Automatic modelling of reaction systems using genetic algorithms and its application to chemical vapour deposition processes: advanced utilizations of simulators for chemical systems

    Microsoft Academic Search

    Takahiro Takahashi; Kimito Funatsu; Yoshinori Ema

    2005-01-01

    The identification of appropriate reaction models is very helpful for developing chemical vapour deposition (CVD) processes. We introduced novel algorithms to analyse experimental data from CVD processes and identify reaction models automatically using genetic algorithms (GAs). The reaction models, which consist of various deposition species and gas-phase and surface reactions, were determined both quantitatively and qualitatively, based on chemical kinetics.

  12. L. Cao, H. Sihler, U. Platt and E. Gutheil: Chemical mechanisms for ozone depletion and halogen release: Supplement 1 1 Chemical reaction mechanisms

    E-print Network

    Meskhidze, Nicholas

    release: Supplement 1 1 Chemical reaction mechanisms: Mechanism for bromine containing species: Reaction kL. Cao, H. Sihler, U. Platt and E. Gutheil: Chemical mechanisms for ozone depletion and halogen [(molec. cm-3 )1-n s-1 ] Reaction order n Reference Reaction No. O3 +h O(1 D)+O2 4.70 10-7 1 Lehrer et al

  13. Heat-Of-Reaction Chemical Heat Pumps--Possible Configurations 

    E-print Network

    Kirol, L. D.

    1986-01-01

    Chemical heat pumps utilize working fluids which undergo reversible chemical changes. Mechanically driven reactive heat pump cycles or, alternatively, heat driven heat pumps in which either heat engine or heat pump working fluid is reactive...

  14. A lattice gas automata model for heterogeneous chemical reactions at mineral surfaces and in pore networks

    SciTech Connect

    Wells, J.T. (Washington Univ., Seattle, WA (USA). Dept. of Geological Sciences); Janecky, D.R.; Travis, B.J. (Los Alamos National Lab., NM (USA))

    1990-01-15

    A lattice gas automata (LGA) model is described, which couples solute transport with chemical reactions at mineral surfaces and in pore networks. Chemical reactions and transport are integrated into a FHP-I LGA code as a module so that the approach is readily transportable to other codes. Diffusion in a box calculations are compared to finite element Fickian diffusion results and provide an approach to quantifying space-time ratios of the models. Chemical reactions at solid surfaces, including precipitation/dissolution, sorption, and catalytic reaction, can be examined with the model because solute diffusion and mineral surface processes are all treated explicitly. The simplicity and flexibility of the LGA approach provides the ability to study the interrelationship between fluid flow and chemical reactions in porous materials, at a level of complexity that has not previously been computationally possible. 20 refs., 8 figs.

  15. SUBSTITUTION REACTIONS FOR THE DETOXIFICATION OF HAZARDOUS CHEMICALS

    EPA Science Inventory

    Chemical Treatment is one of several treatment techniques used for the remediation of toxic and hazardous chemicals. Chemical treatment in this report is defined as substitution of halogens by hydrogens for the conversion of halogenated organic toxicant into its native hydrocarb...

  16. Heat-of-reaction chemical heat pumps: Possible configurations

    Microsoft Academic Search

    L. D. Kirol

    1986-01-01

    Chemical heat pumps utilize working fluids which undergo reversible chemical changes. Mechanically driven reactive heat pump cycles or, alternatively, heat driven heat pumps in which either heat engine or heat pump working fluid is reactive, are considered. As such, chemical heat pumps can be classified by: (1) drive (electric drive, waste heat drive, or prime energy drive), (2) operating mode

  17. Real time monitoring of accelerated chemical reactions by ultrasonication-assisted spray ionization mass spectrometry.

    PubMed

    Lin, Shu-Hsuan; Lo, Ta-Ju; Kuo, Fang-Yin; Chen, Yu-Chie

    2014-01-01

    Ultrasonication has been used to accelerate chemical reactions. It would be ideal if ultrasonication-assisted chemical reactions could be monitored by suitable detection tools such as mass spectrometry in real time. It would be helpful to clarify reaction intermediates/products and to have a better understanding of reaction mechanism. In this work, we developed a system for ultrasonication-assisted spray ionization mass spectrometry (UASI-MS) with an ~1.7 MHz ultrasonic transducer to monitor chemical reactions in real time. We demonstrated that simply depositing a sample solution on the MHz-based ultrasonic transducer, which was placed in front of the orifice of a mass spectrometer, the analyte signals can be readily detected by the mass spectrometer. Singly and multiply charged ions from small and large molecules, respectively, can be observed in the UASI mass spectra. Furthermore, the ultrasonic transducer used in the UASI setup accelerates the chemical reactions while being monitored via UASI-MS. The feasibility of using this approach for real-time acceleration/monitoring of chemical reactions was demonstrated. The reactions of Girard T reagent and hydroxylamine with steroids were used as the model reactions. Upon the deposition of reactant solutions on the ultrasonic transducer, the intermediate/product ions are readily generated and instantaneously monitored using MS within 1 s. Additionally, we also showed the possibility of using this reactive UASI-MS approach to assist the confirmation of trace steroids from complex urine samples by monitoring the generation of the product ions. PMID:24446263

  18. Accelerating chemical reactions: Exploring reactive free-energy surfaces using accelerated ab initio molecular dynamics

    PubMed Central

    Pierce, Levi C. T.; Markwick, Phineus R. L.; McCammon, J. Andrew; Doltsinis, Nikos L.

    2011-01-01

    A biased potential molecular dynamics simulation approach, accelerated molecular dynamics (AMD), has been implemented in the framework of ab initio molecular dynamics for the study of chemical reactions. Using two examples, the double proton transfer reaction in formic acid dimer and the hypothetical adiabatic ring opening and subsequent rearrangement reactions in methylenecyclopropane, it is demonstrated that ab initio AMD can be readily employed to efficiently explore the reactive potential energy surface, allowing the prediction of chemical reactions and the identification of metastable states. An adaptive variant of the AMD method is developed, which additionally affords an accurate representation of both the free-energy surface and the mechanism associated with the chemical reaction of interest and can also provide an estimate of the reaction rate. PMID:21548673

  19. Reactions of hydrazines with chemicals found in environment. Technical report

    SciTech Connect

    Judeikis, H.S.; Damschen, D.E.

    1992-01-24

    Reactions of hydrazine, monomethylhydrazine and unsymmetrical dimethylhydrazine with selected species of interest that are found in the environment have been investigated. Included are aqueous phase reactions that can occur in atmospheric aerosols, groundwater, or soils in contact with groundwater, as well as selected gas phase reactions. Reactants include oxygen and hydrogen peroxide (both reactants in the presence and absence of catalysts), ozone, nitrous acid, sulfur dioxide, and acetone (as a model for environmental ketones and aldehydes). Rate constants for the reactions have been determined, or upper limits set. In several instances, reaction products have been identified. By far, the fastest reactions measured were those involving the hydrazines and ozone with (second-order) rate constants up to 2.4 x 107 liter/mole-sec.

  20. Mixing and chemical reaction in sheared and nonsheared homogeneous turbulence

    NASA Technical Reports Server (NTRS)

    Leonard, Andy D.; Hill, James C.

    1992-01-01

    Direct numerical simulations were made to examine the local structure of the reaction zone for a moderately fast reaction between unmixed species in decaying, homogeneous turbulence and in a homogeneous turbulent shear flow. Pseudospectral techniques were used in domains of 64 exp 3 and higher wavenumbers. A finite-rate, single step reaction between non-premixed reactants was considered, and in one case temperature-dependent Arrhenius kinetics was assumed. Locally intense reaction rates that tend to persist throughout the simulations occur in locations where the reactant concentration gradients are large and are amplified by the local rate of strain. The reaction zones are more organized in the case of a uniform mean shear than in isotropic turbulence, and regions of intense reaction rate appear to be associated with vortex structures such as horseshoe vortices and fingers seen in mixing layers. Concentration gradients tend to align with the direction of the most compressive principal strain rate, more so in the isotropic case.

  1. FT-ICR Study of Chemical Reaction of Precursor Clusters of SWNT Masamichi Kohno, Shuhei Inoue and Shigeo Maruyama

    E-print Network

    Maruyama, Shigeo

    FT-ICR Study of Chemical Reaction of Precursor Clusters of SWNT Masamichi Kohno, Shuhei Inoue and Shigeo Maruyama Chemical reaction of carbon clusters and metal-carbon binary clusters (MCn , M = Ni or Co

  2. Reduction of detonating liquid nitromethane's chemical reaction-zone length by chemical sensitization

    NASA Astrophysics Data System (ADS)

    Engelke, Ray; Sheffield, Stephen A.; Stacy, Howard L.; Quintana, John P.

    2005-09-01

    We examine the effect of the addition of small amounts of the organic base diethylenetriamine [NH2(CH2CH2)NH(CH2CH2)NH2] on the chemical reaction-zone length (CRZ) of detonating liquid nitromethane (CH3NO2). This is done by making accurate measurements of the detonating materials' diameter-effect curves (i.e., detonation speed versus lateral charge size) as a function of the amount of chemical sensitizer added. Detonation speed experiments were performed with additions of the organic base in amounts between 0.00 and 0.25wt%. Reductions in the CRZ of as much as 25% were produced by base addition. Most of the reduction in length is produced by very small amounts of base addition—i.e., ca. 0.05wt% of base or less (i.e., 1 molecule of the base per 3300 nitromethane molecules or less). Measured detonation speeds are given for five compositions of nitromethane and base as a function of charge internal diameter. Absolute CRZs are estimated using a value of liquid nitromethane's CRZ obtained by other means. Earlier work has determined a relationship between the failure diameter of sensitized nitromethane compositions and the amount of base addition. Here we have found a relationship between relative CRZ and the amount of base addition. By eliminating the base parameterization, we give a phenomenological relationship between the failure diameter of such materials and their steady one-dimensional CRZs.

  3. Tattoo-Associated Skin Reaction: The Importance of an Early Diagnosis and Proper Treatment

    PubMed Central

    Bassi, Andrea; Campolmi, Piero; Cannarozzo, Giovanni; Conti, Rossana; Bruscino, Nicola; Gola, Massimo; Ermini, Stefano; Massi, Daniela; Moretti, Silvia

    2014-01-01

    Tattoo is going to be a very common practice especially among young people and we are witnessing a gradual increase of numerous potential complications to tattoo placement which are often seen by physicians, but generally unknown to the public. The most common skin reactions to tattoo include a transient acute inflammatory reaction due to trauma of the skin with needles and medical complications such as superficial and deep local infections, systemic infections, allergic contact dermatitis, photodermatitis, granulomatous and lichenoid reactions, and skin diseases localized on tattooed area (eczema, psoriasis, lichen, and morphea). Next to these inflammatory skin reactions we have to consider also the possibility of the development of cutaneous conditions such as pseudolymphomatous reactions and pseudoepitheliomatous hyperplasia. The aim of this study is to underline the importance of an early diagnosis by performing a histological examination especially when we are in front of suspected papulonodular lesions arising from a tattoo, followed by a proper treatment, since cutaneous neoplastic evolution is known to be a rare but possible complication. PMID:25147796

  4. CHEMICAL PROCESSES IN PROTOPLANETARY DISKS. II. ON THE IMPORTANCE OF PHOTOCHEMISTRY AND X-RAY IONIZATION

    SciTech Connect

    Walsh, Catherine; Millar, T. J. [Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN (United Kingdom); Nomura, Hideko [Department of Astronomy, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Aikawa, Yuri, E-mail: catherine.walsh@qub.ac.uk [Department of Earth and Planetary Sciences, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe 657-8501 (Japan)

    2012-03-10

    We investigate the impact of photochemistry and X-ray ionization on the molecular composition of, and ionization fraction in, a protoplanetary disk surrounding a typical T Tauri star. We use a sophisticated physical model, which includes a robust treatment of the radiative transfer of UV and X-ray radiation, and calculate the time-dependent chemical structure using a comprehensive chemical network. In previous work, we approximated the photochemistry and X-ray ionization; here, we recalculate the photoreaction rates using the explicit UV wavelength spectrum and wavelength-dependent reaction cross sections. We recalculate the X-ray ionization rate using our explicit elemental composition and X-ray energy spectrum. We find that photochemistry has a larger influence on the molecular composition than X-ray ionization. Observable molecules sensitive to the photorates include OH, HCO{sup +}, N{sub 2}H{sup +}, H{sub 2}O, CO{sub 2}, and CH{sub 3}OH. The only molecule significantly affected by the X-ray ionization is N{sub 2}H{sup +}, indicating that it is safe to adopt existing approximations of the X-ray ionization rate in typical T Tauri star-disk systems. The recalculation of the photorates increases the abundances of neutral molecules in the outer disk, highlighting the importance of taking into account the shape of the UV spectrum in protoplanetary disks. A recalculation of the photoreaction rates also affects the gas-phase chemistry due to the adjustment of the H/H{sub 2} and C{sup +}/C ratios. The disk ionization fraction is not significantly affected by the methods adopted to calculate the photochemistry and X-ray ionization. We determine that there is a probable 'dead zone' where accretion is suppressed, present in a layer, Z/R {approx}< 0.1-0.2, in the disk midplane, within R Almost-Equal-To 200 AU.

  5. Product-state control of bi-alkali-metal chemical reactions

    SciTech Connect

    Meyer, Edmund R.; Bohn, John L. [JILA, NIST, and University of Colorado, Department of Physics, Boulder, Colorado 80309-0440 (United States)

    2010-10-15

    We consider ultracold, chemically reactive scattering collisions of the diatomic molecules KRb. When two such molecules collide in an ultracold gas, we find that they are energetically forbidden from reacting to form the trimer species K{sub 2}Rb or Rb{sub 2}K, and hence can only react via the bond-swapping reaction 2KRb{yields}K{sub 2}+Rb{sub 2}. Moreover, the tiny energy released in this reaction can in principle be set to zero by applying electric or microwave fields, implying a means of controlling the available reaction channels in a chemical reaction.

  6. Chemoselectivity in Chemical Biology: Acyl Transfer Reactions with Sulfur and Selenium

    PubMed Central

    2012-01-01

    A critical source of insight into biological function is derived from the chemist’s ability to create new covalent bonds between molecules, whether they are endogenous or exogenous to a biological system. A daunting impediment to selective bond formation, however, is the myriad of reactive functionalities present in biological milieu. The high reactivity of the most abundant molecule in biology, water, makes the challenges all the more difficult. We have met these challenges by exploiting the reactivity of sulfur and selenium in acyl transfer reactions. The reactivity of both sulfur and selenium is high compared with that of their chalcogen congener, oxygen. In this Account, we highlight recent developments in this arena, emphasizing contributions from our laboratory. One focus of our research is furthering the chemistry of native chemical ligation (NCL) and expressed protein ligation (EPL), two related processes that enable the synthesis and semisynthesis of proteins. These techniques exploit the lower pKa of thiols and selenols relative to alcohols. Although a deprotonated hydroxyl group in the side chain of a serine residue is exceedingly rare in a biological context, the pKa values of the thiol in cysteine (8.5) and of the selenol in selenocysteine (5.7) often render these side chains anionic under physiological conditions. NCL and EPL take advantage of the high nucleophilicity of the thiolate as well as its utility as a leaving group, and we have expanded the scope of these methods to include selenocysteine. Although the genetic code limits the components of natural proteins to 20 or so ?-amino acids, NCL and EPL enable the semisynthetic incorporation of a limitless variety of nonnatural modules into proteins. These modules are enabling chemical biologists to interrogate protein structure and function with unprecedented precision. We are also pursuing the further development of the traceless Staudinger ligation, through which a phosphinothioester and azide form an amide. We first reported this chemical ligation method, which leaves no residual atoms in the product, in 2000. Our progress in effecting the reaction in water, without an organic cosolvent, was an important step in the expansion of its utility. Moreover, we have developed the traceless Staudinger reaction as a means for immobilizing proteins on a solid support, providing a general method of fabricating microarrays that display proteins in a uniform orientation. Along with NCL and EPL, the traceless Staudinger ligation has made proteins more readily accessible targets for chemical synthesis and semisynthesis. The underlying acyl transfer reactions with sulfur and selenium provide an efficient means to synthesize, remodel, and immobilize proteins, and they have enabled us to interrogate biological systems. PMID:21639109

  7. Noise-Induced Modulation of the Relaxation Kinetics around a Non-Equilibrium Steady State of Non-Linear Chemical Reaction Networks

    Microsoft Academic Search

    Rajesh Ramaswamy; Ivo F. Sbalzarini; Nélido González-Segredo

    2011-01-01

    Stochastic effects from correlated noise non-trivially modulate the kinetics of non-linear chemical reaction networks. This is especially important in systems where reactions are confined to small volumes and reactants are delivered in bursts. We characterise how the two noise sources confinement and burst modulate the relaxation kinetics of a non-linear reaction network around a non-equilibrium steady state. We find that

  8. CHEMICAL REACTIONS OF AQUATIC HUMIC MATERIALS WITH SELECTED OXIDANTS

    EPA Science Inventory

    A study was conducted to identify the specific organic reaction products of natural aquatic humic materials with selected oxidants (KMnO4, HOCl, Cl02, O3 and monochloramine). Reaction products were identified by GC/MS after solvent extraction and derivatization. The two most reac...

  9. Energy storage and transport by reversible chemical reactions

    Microsoft Academic Search

    G. Beghi

    1987-01-01

    Reversible thermochemical reactions are one of the possibilities to store and transport high temperature heat (800 K up to 1300 K). There are open cycles and closed cycles. Some reversible systems are described, as the SO2-SO3 system. A typical example of open cycle is the reaction for water decomposition. Results of a pilot plant to verify the decomposition of sulfuric

  10. Fall-Off from Extrapolated Values of All Chemical Reactions at Very High Temperatures

    PubMed Central

    Eyring, Henry; Leu, An-Lu

    1975-01-01

    At high temperatures the breaking of chemical bonds becomes relatively easy and the slow step in a chemical reaction shifts to the rate at which energy can seep into the bond that is to break. This has been observed by various investigators. A new general theory of reactions is developed here to explain this limiting rate at high temperatures. In the case of cyclopropane and cyclobutane the theory leads to the conclusion that 20 degrees of freedom form a heat reservoir which feeds the energy into the carbon bond that is to break and that this rate becomes controlling above about 1200°K. This would correspond to 20 of the 21 vibrational bonds of cyclopropane feeding energy into the carbon bond that is to break, and there would be no noticeable rise in the number of bonds for cyclobutane. This theory is especially important for shock tubes and detonations, where this falling-off from the extrapolated low temperature rate becomes glaringly obvious. PMID:16578725

  11. Real World of Industrial Chemistry: Ethylene: The Organic Chemical Industry's Most Important Building Block.

    ERIC Educational Resources Information Center

    Fernelius, W. Conrad, Ed.; And Others

    1979-01-01

    The value of ethylene, as the organic chemical industry's most important building block, is discussed. The discussion focuses on the source of ethylene, its various forms and functions, and the ways in which the forms are made. (SA)

  12. Noise-induced enhancement of chemical reactions in nonlinear flows Zonghua Liu, Ying-Cheng Lai,a)

    E-print Network

    Lopez, John M.

    Noise-induced enhancement of chemical reactions in nonlinear flows Zonghua Liu, Ying-Cheng Lai consider chemical reactions of the general type: A B2C, in idealized two-dimensional nonlinear flows of noise. We find that noise can significantly enhance the chemical reaction in a resonancelike manner

  13. Ion-neutral chemical reactions between ultracold localized ions and neutral molecules with single-particle resolution

    E-print Network

    Schiller, Stephan

    Ion-neutral chemical reactions between ultracold localized ions and neutral molecules with single-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany Received 23 January 2006; published 19 April 2006 Chemical reactions characterization of a chemical reaction in which neither one of the reactants nor the product is directly

  14. THE JOURNAL OF CHEMICAL PHYSICS 133, 224101 (2010) Steepest descent reaction path integration using a first-order

    E-print Network

    Schlegel, H. Bernhard

    2010-01-01

    THE JOURNAL OF CHEMICAL PHYSICS 133, 224101 (2010) Steepest descent reaction path integration using; accepted 20 October 2010; published online 8 December 2010) The theoretical treatment of chemical reactions surface and five chemical reactions. The use of Hessian updating, as a means for reducing the overall

  15. A combined quantum-classical dynamics method for calculating thermal rate constants of chemical reactions in solution

    E-print Network

    Truong, Thanh N.

    -flux correlation function for calculating the thermal rate constants of chemical reactions in solution in this study would provide a complete tool for studying the quantum dynamics of chemical reactions the thermal chemical reaction rate constants. Furthermore, we also employ an efficient and accurate quantum

  16. Optimal behavior of consecutive chemical reactions Thor A. Bak1, Peter Salamon2, Bjarne Andresen2,3

    E-print Network

    Salamon, Peter

    Optimal behavior of consecutive chemical reactions ABC Thor A. Bak1, Peter Salamon2, Bjarne The consecutive chemical reactions ABC are analyzed both numerically and analytically using temperature-11] considered the question of improving the yield of a chemical reaction taking place in a tubular reactor

  17. JOURNAL OF RESEARCH IN SCIENCE TEACHING VOL. 45, NO. 7, PP. 771793 (2008) Classification of Chemical Reactions: Stages of Expertise

    E-print Network

    Talanquer, Vicente A.

    2008-01-01

    of Chemical Reactions: Stages of Expertise Marilyne Stains, Vicente Talanquer Department of Chemistry attention when classifying chemical reactions at the symbolic and microscopic levels. We identified the categories that students create when classifying chemical reactions, and compared the performance in simple

  18. Role of Conformational Structures and Torsional Anharmonicity in Controlling Chemical Reaction Rates and Relative Yields: Butanal + HO2 Reactions

    SciTech Connect

    Zheng, Jingjing; Seal, Prasenjit; Truhlar, Donald G.

    2013-01-01

    Aldehyde–radical reactions are important in atmospheric and combustion chemistry, and the reactions studied here also serve more generally to illustrate a fundamental aspect of chemical kinetics that has been relatively unexplored from a quantitative point of view, in particular the roles of multiple structures and torsional anharmonicity in determining the rate constants and branching ratios (product yields). We consider hydrogen abstraction from four carbon sites of butanal (carbonyl-C, a-C, b-C and g-C) by hydroperoxyl radical. We employed multi-structural variational transition state theory for studying the first three channels; this uses a multi-faceted dividing surface and allows us to include the contributions of multiple structures of both reacting species and transition states. Multiconfigurational Shepard interpolation (MCSI) was used to obtain the geometries and energies of the potential energy surface along the minimum-energy paths, with gradients and Hessians calculated by the M08-HX/maug-cc-pVTZ method. We find the numbers of structures obtained for the transition states are 46, 60, 72 and 76respectively for the H abstraction at the carbonyl C, the a position, the b position and the g position. Our results show that neglecting the factors arising from multiple structures and torsional anharmonicity would lead to errors at 300, 1000 and 2400 K of factors of 8, 11 and 10 for abstraction at the carbonyl-O, 2, 11 and 25 at the a-C position, 2, 23 and 47 at the b-C position, and 0.6, 8 and 18 at the g-C position. The errors would be even larger at high temperature for the reverse of the H abstraction at the b-C. Relative yields are changed as much as a factor of 7.0 at 200 K, a factor of 5.0 at 298 K, and a factor of 3.7 in the other direction at 2400 K. The strong dependence of the product ratios on the multi-structural anharmonicity factors shows that such factors play an important role in controlling branching ratios in reaction mechanism networks.

  19. Extraction of chemical structures and reactions from the literature

    E-print Network

    Lowe, Daniel Mark

    2012-10-09

    Entities of Biological Interest CIP = Cahn-Ingold-Prelog CML = Chemical Markup Language DTD = Document Type Definition EPO = European Patent Office InChI = IUPAC International Chemical Identifier IPC = International Patent Classification IUPAC... ................................................................................................ 121 3.2.16 Output formats ...................................................................................................... 124 3.2.16.1 CML...

  20. Conceptual Reorganization and the Construction of the Chemical Reaction Concept during Secondary Education.

    ERIC Educational Resources Information Center

    Stavridou, Heleni; Solomonidou, Christina

    1998-01-01

    Studies aspects of the conceptual reorganization and change of students aged 12-18 (N=40). Describes conceptual change through case studies and students' identifications of chemical reactions. Contains 18 references. (DDR)

  1. Descriptive Simulation: Combining Symbolic and Numerical Methods in the Analysis of Chemical Reaction Mechanisms

    E-print Network

    Eisenberg, Michael

    1989-09-01

    The Kineticist's Workbench is a computer program currently under development whose purpose is to help chemists understand, analyze, and simplify complex chemical reaction mechanisms. This paper discusses one module ...

  2. The Kineticist's Workbench: Combining Symbolic and Numerical Methods in the Simulation of Chemical Reaction Mechanisms

    E-print Network

    Eisenberg, Michael A.

    1991-05-01

    The Kineticist's Workbench is a program that simulates chemical reaction mechanisms by predicting, generating, and interpreting numerical data. Prior to simulation, it analyzes a given mechanism to predict that ...

  3. Coherent chemical kinetics as quantum walks I: Reaction operators for radical pairs

    E-print Network

    A. Chia; A. Gorecka; K. C. Tan; L. Pawela; P. Kurzynski; T. Paterek; D. Kaszlikowski

    2015-06-13

    Classical chemical kinetics use rate-equation models to describe how a reaction proceeds in time. Such models are sufficient for describing state transitions in a reaction where coherences between different states do not arise, or in other words, a reaction which contain only incoherent transitions. A prominent example reaction containing coherent transitions is the radical-pair model. The kinetics of such reactions is defined by the so-called reaction operator which determines the radical-pair state as a function of intermediate transition rates. We argue that the well-known concept of quantum walks from quantum information theory is a natural and apt framework for describing multisite chemical reactions. By composing Kraus maps that act only on two sites at a time, we show how the quantum-walk formalism can be applied to derive a reaction operator for the standard avian radical-pair reaction. Our reaction operator predicts a recombination dephasing rate consistent with recent experiments [J. Chem. Phys. {\\bf 139}, 234309 (2013)], in contrast to previous work by Jones and Hore [Chem. Phys. Lett. {\\bf 488}, 90 (2010)]. The standard radical-pair reaction has conventionally been described by either a normalised density operator incorporating both the radical pair and reaction products, or by a trace-decreasing density operator that considers only the radical pair. We demonstrate a density operator that is both normalised and refers only to radical-pair states. Generalisations to include additional dephasing processes and an arbitrary number of sites are also discussed.

  4. RPMDrate: Bimolecular chemical reaction rates from ring polymer molecular dynamics

    E-print Network

    Suleimanov, Yu.V.

    We present RPMDrate, a computer program for the calculation of gas phase bimolecular reaction rate coefficients using the ring polymer molecular dynamics (RPMD) method. The RPMD rate coefficient is calculated using the ...

  5. Efficiency of a stirred chemical reaction in a closed vessel

    E-print Network

    Cristobal lopez; Davide Vergni; Angelo Vulpiani

    2002-01-22

    We perform a numerical study of the reaction efficiency in a closed vessel. Starting with a little spot of product, we compute the time needed to complete the reaction in the container following an advection-reaction-diffusion process. Inside the vessel it is present a cellular velocity field that transports the reactants. If the size of the container is not very large compared with the typical length of the velocity field one has a plateau of the reaction time as a function of the strength of the velocity field, $U$. This plateau appears both in the stationary and in the time-dependent flow. A comparison of the results for the finite system with the infinite case (for which the front speed, $v_f$, gives a simple estimate of the reacting time) shows the dramatic effect of the finite size.

  6. Large-scale prediction of adverse drug reactions using chemical, biological, and phenotypic properties of drugs

    PubMed Central

    Liu, Mei; Wu, Yonghui; Chen, Yukun; Sun, Jingchun; Zhao, Zhongming; Chen, Xue-wen; Matheny, Michael Edwin

    2012-01-01

    Objective Adverse drug reaction (ADR) is one of the major causes of failure in drug development. Severe ADRs that go undetected until the post-marketing phase of a drug often lead to patient morbidity. Accurate prediction of potential ADRs is required in the entire life cycle of a drug, including early stages of drug design, different phases of clinical trials, and post-marketing surveillance. Methods Many studies have utilized either chemical structures or molecular pathways of the drugs to predict ADRs. Here, the authors propose a machine-learning-based approach for ADR prediction by integrating the phenotypic characteristics of a drug, including indications and other known ADRs, with the drug's chemical structures and biological properties, including protein targets and pathway information. A large-scale study was conducted to predict 1385 known ADRs of 832 approved drugs, and five machine-learning algorithms for this task were compared. Results This evaluation, based on a fivefold cross-validation, showed that the support vector machine algorithm outperformed the others. Of the three types of information, phenotypic data were the most informative for ADR prediction. When biological and phenotypic features were added to the baseline chemical information, the ADR prediction model achieved significant improvements in area under the curve (from 0.9054 to 0.9524), precision (from 43.37% to 66.17%), and recall (from 49.25% to 63.06%). Most importantly, the proposed model successfully predicted the ADRs associated with withdrawal of rofecoxib and cerivastatin. Conclusion The results suggest that phenotypic information on drugs is valuable for ADR prediction. Moreover, they demonstrate that different models that combine chemical, biological, or phenotypic information can be built from approved drugs, and they have the potential to detect clinically important ADRs in both preclinical and post-marketing phases. PMID:22718037

  7. A new class of highly efficient exact stochastic simulation algorithms for chemical reaction networks

    Microsoft Academic Search

    Rajesh Ramaswamy; Ne´lido Gonza´lez-Segredo; Ivo F. Sbalzarini

    2009-01-01

    We introduce an alternative formulation of the exact stochastic simulation algorithm (SSA) for sampling trajectories of the chemical master equation for a well-stirred system of coupled chemical reactions. Our formulation is based on factored-out, partial reaction propensities. This novel exact SSA, called the partial-propensity direct method (PDM), is highly efficient and has a computational cost that scales at most linearly

  8. Kinetics of thermochemical gas-solid reactions important in the Venus sulfur cycle

    NASA Technical Reports Server (NTRS)

    Fegley, Bruce, Jr.

    1988-01-01

    The thermochemical net reaction CaCO3 + SO2 yields CaSO4 + CO is predicted to be an important sink for incorporation of SO2 into the Venus crust. The reaction rate law was established to understand the dependence of rate on experimental variables such as temperature and partial pressure of SO2, CO2, and O2. The experimental approach was a variant of the thermogravimetric method often employed to study the kinetics of thermochemical gas-solid reactions. Clear calcite crystals were heated at constant temperature in SO2-bearing gas streams for varying time periods. Reaction rate was determined by three independent methods. A weighted linear least squares fit to all rate data yielded a rate equation. Based on the Venera 13, 14 and Vega 2 observations of CaO content of the Venus atmosphere, SO2 at the calculated rate would be removed from the Venus atmosphere in about 1,900,00 years. The most plausible endogenic source of the sulfur needed to replenish atmospheric SO2 is volcanism. The annual amount of erupted material needed for the replenishment depends on sulfur content; three ratios are used to calculate rates ranging from 0.4 to 11 cu km/year. This geochemically derived volcanism rate can be used to test if geophysically derived rates are correct. The work also suggests that Venus is less volcanically active than the Earth.

  9. Ambient solid-state mechano-chemical reactions between functionalized carbon nanotubes

    PubMed Central

    Kabbani, Mohamad A.; Tiwary, Chandra Sekhar; Autreto, Pedro A.S.; Brunetto, Gustavo; Som, Anirban; Krishnadas, K.R.; Ozden, Sehmus; Hackenberg, Ken P.; Gong, Yongi; Galvao, Douglas S.; Vajtai, Robert; Kabbani, Ahmad T.; Pradeep, Thalappil; Ajayan, Pulickel M.

    2015-01-01

    Carbon nanotubes can be chemically modified by attaching various functionalities to their surfaces, although harsh chemical treatments can lead to their break-up into graphene nanostructures. On the other hand, direct coupling between functionalities bound on individual nanotubes could lead to, as yet unexplored, spontaneous chemical reactions. Here we report an ambient mechano-chemical reaction between two varieties of nanotubes, carrying predominantly carboxyl and hydroxyl functionalities, respectively, facilitated by simple mechanical grinding of the reactants. The purely solid-state reaction between the chemically differentiated nanotube species produces condensation products and unzipping of nanotubes due to local energy release, as confirmed by spectroscopic measurements, thermal analysis and molecular dynamic simulations. PMID:26073564

  10. Relationship between Thermodynamic Driving Force and One-Way Fluxes in Reversible Chemical Reactions

    E-print Network

    Daniel A. Beard; Hong Qian

    2006-11-22

    Chemical reaction systems operating in nonequilibrium open-system states arise in a great number of contexts, including the study of living organisms, in which chemical reactions, in general, are far from equilibrium. Here we introduce a theorem that relates forward and re-verse fluxes and free energy for any chemical process operating in a steady state. This rela-tionship, which is a generalization of equilibrium conditions to the case of a chemical process occurring in a nonequilibrium steady state, provides a novel equivalent definition for chemical reaction free energy. In addition, it is shown that previously unrelated theories introduced by Ussing and Hodgkin and Huxley for transport of ions across membranes, Hill for catalytic cycle fluxes, and Crooks for entropy production in microscopically reversible systems, are united in a common framework based on this relationship.

  11. Ambient solid-state mechano-chemical reactions between functionalized carbon nanotubes.

    PubMed

    Kabbani, Mohamad A; Tiwary, Chandra Sekhar; Autreto, Pedro A S; Brunetto, Gustavo; Som, Anirban; Krishnadas, K R; Ozden, Sehmus; Hackenberg, Ken P; Gong, Yongi; Galvao, Douglas S; Vajtai, Robert; Kabbani, Ahmad T; Pradeep, Thalappil; Ajayan, Pulickel M

    2015-01-01

    Carbon nanotubes can be chemically modified by attaching various functionalities to their surfaces, although harsh chemical treatments can lead to their break-up into graphene nanostructures. On the other hand, direct coupling between functionalities bound on individual nanotubes could lead to, as yet unexplored, spontaneous chemical reactions. Here we report an ambient mechano-chemical reaction between two varieties of nanotubes, carrying predominantly carboxyl and hydroxyl functionalities, respectively, facilitated by simple mechanical grinding of the reactants. The purely solid-state reaction between the chemically differentiated nanotube species produces condensation products and unzipping of nanotubes due to local energy release, as confirmed by spectroscopic measurements, thermal analysis and molecular dynamic simulations. PMID:26073564

  12. Signatures of chemical reactions in the morphology and fluctuations of giant vesicles

    NASA Astrophysics Data System (ADS)

    Döbereiner, Hans-Günther; Petrov, Peter G.; Riske, Karin A.

    2003-01-01

    The behaviour of an amphiphilic membrane is determined by the physical and chemical properties of the molecules which form the bilayer and their interactions with the surrounding medium. Bulk or interfacial chemical reactions modify interaction parameters and/or affect directly the chemical composition of the membrane. We monitor the morphological response and the thermal fluctuations of giant lipid vesicles to chemical reactions in the external vesicle medium using phase-contrast microscopy. Observation of vesicle conformations as a function of time allows us to characterize the statics and dynamics of membrane response as well as the underlying chemical kinetics. As two examples, we present (a) a photochemical reaction of hexacyanoferrate which induces an increase in pH and (b) the enzymatic cleavage of phosphatidyl choline by the phospholipase C from Bacillus cereus.

  13. Light-induced nitrous acid (HONO) production from NO2 heterogeneous reactions on household chemicals

    NASA Astrophysics Data System (ADS)

    Gómez Alvarez, Elena; Sörgel, Matthias; Gligorovski, Sasho; Bassil, Sabina; Bartolomei, Vincent; Coulomb, Bruno; Zetzsch, Cornelius; Wortham, Henri

    2014-10-01

    Nitrous acid (HONO) can be generated in various indoor environments directly during combustion processes or indirectly via heterogeneous NO2 reactions with water adsorbed layers on diverse surfaces. Indoors not only the concentrations of NO2 are higher but the surface to volume (S/V) ratios are larger and therefore the potential of HONO production is significantly elevated compared to outdoors. It has been claimed that the UV solar light is largely attenuated indoors. Here, we show that solar light (? > 340 nm) penetrates indoors and can influence the heterogeneous reactions of gas-phase NO2 with various household surfaces. The NO2 to HONO conversion mediated by light on surfaces covered with domestic chemicals has been determined at atmospherically relevant conditions i.e. 50 ppb NO2 and 50% RH. The formation rates of HONO were enhanced in presence of light for all the studied surfaces and are determined in the following order: 1.3·109 molecules cm-2 s-1 for borosilicate glass, 1.7·109 molecules cm-2 s-1 for bathroom cleaner, 1.0·1010 molecules cm-2 s-1 on alkaline detergent (floor cleaner), 1.3·1010 molecules cm-2 s-1 for white wall paint and 2.7·1010 molecules cm-2 s-1 for lacquer. These results highlight the potential of household chemicals, used for cleaning purposes to generate HONO indoors through light-enhanced NO2 heterogeneous reactions. The results obtained have been applied to predict the timely evolution of HONO in a real indoor environment using a dynamic mass balance model. A steady state mixing ratio of HONO has been estimated at 1.6 ppb assuming a contribution from glass, paint and lacquer and considering the photolysis of HONO as the most important loss process.

  14. Investigation of electron density changes at the onset of a chemical reaction using the state-specific dual descriptor from conceptual density functional theory.

    PubMed

    De Proft, Frank; Forquet, Valérian; Ourri, Benjamin; Chermette, Henry; Geerlings, Paul; Morell, Christophe

    2015-04-14

    The electron density changes from reactants towards the transition state of a chemical reaction is expressed as a linear combination of the state-specific dual descriptors (SSDD) of the corresponding reactant complexes. Consequently, the SSDD can be expected to bear important resemblance to the so-called natural orbitals for chemical valence (NOCV), introduced as the orbitals that diagonalize the deformation density matrix of interacting molecules. This agreement is shown for three case studies: the complexation of a Lewis acid with a Lewis base, a SN2 nucleophilic substitution reaction and a Diels-Alder cycloaddition reaction. As such, the SSDD computed for reactant complexes are shown to provide important information about charge transfer interactions during a chemical reaction. PMID:25760399

  15. Effects of reversible chemical reaction on Li diffusion and stresses in spherical composition-gradient electrodes

    NASA Astrophysics Data System (ADS)

    Li, Yong; Zhang, Kai; Zheng, Bailin; Zhang, Xiaoqian; Wang, Qi

    2015-06-01

    Composition-gradient electrode materials have been proven to be one of the most promising materials in lithium-ion battery. To study the mechanism of mechanical degradation in spherical composition-gradient electrodes, the finite deformation theory and reversible chemical theory are adopted. In homogeneous electrodes, reversible electrochemical reaction may increase the magnitudes of stresses. However, reversible electrochemical reaction has different influences on stresses in composition-gradient electrodes, resulting from three main inhomogeneous factors—forward reaction rate, backward reaction rate, and reaction partial molar volume. The decreasing transition form of forward reaction rate, increasing transition form of backward reaction rate, and increasing transition form of reaction partial molar volume can reduce the magnitudes of stresses. As a result, capacity fading and mechanical degradation are reduced by taking advantage of the effects of inhomogeneous factors.

  16. Analytical Solution of Steady State Equations for Chemical Reaction Networks with Bilinear Rate Laws

    PubMed Central

    Halász, Ádám M.; Lai, Hong-Jian; McCabe, Meghan M.; Radhakrishnan, Krishnan; Edwards, Jeremy S.

    2014-01-01

    True steady states are a rare occurrence in living organisms, yet their knowledge is essential for quasi-steady state approximations, multistability analysis, and other important tools in the investigation of chemical reaction networks (CRN) used to describe molecular processes on the cellular level. Here we present an approach that can provide closed form steady-state solutions to complex systems, resulting from CRN with binary reactions and mass-action rate laws. We map the nonlinear algebraic problem of finding steady states onto a linear problem in a higher dimensional space. We show that the linearized version of the steady state equations obeys the linear conservation laws of the original CRN. We identify two classes of problems for which complete, minimally parameterized solutions may be obtained using only the machinery of linear systems and a judicious choice of the variables used as free parameters. We exemplify our method, providing explicit formulae, on CRN describing signal initiation of two important types of RTK receptor-ligand systems, VEGF and EGF-ErbB1. PMID:24334389

  17. Non-stationary filtration mode during chemical reactions with the gas phase

    NASA Astrophysics Data System (ADS)

    Zavialov, Ivan; Konyukhov, Andrey; Negodyaev, Sergey

    2015-04-01

    An experimental and numerical study of filtration accompanied by chemical reactions between displacing fluid and solid skeleton is considered. Glass balls (400-500 ?m in diameter) were placed in 1 cm gap between two glass sheets and were used as model porous medium. The baking soda was added to the glass balls. The 70% solution of acetic acid was used as the displacer. The modeling porous medium was saturated with a mineral oil, and then 70% solution of colored acetic acid was pumped through the medium. The glass balls and a mineral oil have a similar refractive index, so the model porous medium was optically transparent. During the filtration, the gas phase was generated by the chemical reactions between the baking soda and acetic acid, and time-dependent displacement of the chemical reaction front was observed. The front of the chemical reaction was associated with the most intensive gas separation. The front moved, stopped, and then moved again to the area where it had been already. We called this process a secondary oxidation wave. To describe this effect, we added to the balance equations a term associated with the formation and disappearance of phases due to chemical reactions. The equations were supplemented by Darcy's law for multiphase filtration. Nonstationarity front propagation of the chemical reaction in the numerical experiment was observed at Damköhler numbers greater than 100. The mathematical modelling was agreed well with the experimental results.

  18. Computer simulation of diffusion-limited chemical reactions in three dimensions

    SciTech Connect

    Torney, D.C.; Warnock, T.T.; Kollman, P.

    1987-01-01

    Rates of transient diffusion-limited chemical reactions in three dimensions are determined by Monte Carlo computer simulation. Particles are initially placed at random on a cubic periodic Euclidean lattice and perform independent random walks. Pairs of particles arriving at the same site are reacted according to the rules of particular types of chemical reaction; annihilation, bimolecular, and catalytic reactions are simulated. The computational method involves searching partially ordered lists of the particles' coordinates, to find any particles sharing a lattice site. The authors observe the effects of the diffusion coefficients and the stoichiometry of the reactive species on the rate of reaction. The results strongly support the contention that the Smoluchowski-Noyes theory does not give a uniformly accurate prediction of diffusion-limited reaction rates in three dimensions. The only case of substantial disagreement between the simulation results and the theory is found for nearly equimolar bimolecular reaction.

  19. Unraveling the chemical dynamics of bimolecular reactions of ground state boron atoms, B(2

    E-print Network

    Kaiser, Ralf I.

    Unraveling the chemical dynamics of bimolecular reactions of ground state boron atoms, B(2 PjArticle on the web 8th March 2004 The reaction dynamics of atomic boron, B(2 P), with acetylene, C2H2(X 1 Sg þ molecular beams technique. Only the atomic boron versus hydrogen atom exchange pathway was observed. Forward

  20. Mechanism and Chemical Reaction of Fly Ash Geopolymer Cement A Review

    Microsoft Academic Search

    A. M. Mustafa Al Bakri; H. Kamarudin; M. Bnhussain; I. Khairul Nizar; W. I. W. Mastura

    2011-01-01

    This paper presents the work carried out on the chemical reaction, mechanism, role of materials, applications and microstructure of fly ash geopolymer cement. Geopolymeris a type of amorphous alumino-silicate cementitious material. Geopolymer can besynthesized by polycondensation reaction of geopolymeric precursor, and alkalipolysilicates. Literature demonstrates that the exact geopolymerization mechanism is not well understood because the geopolymerization process involves a substantially

  1. Acidbase chemical reaction model for nucleation rates in the polluted atmospheric boundary layer

    E-print Network

    Acid­base chemical reaction model for nucleation rates in the polluted atmospheric boundary layer for modeling nucleation rates, based on a sequence of acid­base reactions. The model uses empirical estimates- spheric boundary layer are positively correlated with concentra- tions of sulfuric acid vapor. However

  2. Simulation of chemical reaction via particle tracking: Diffusion-limited versus thermodynamic rate-limited regimes

    Microsoft Academic Search

    David A. Benson; Mark M. Meerschaert

    2008-01-01

    Chemical reactions may be simulated without regard to local concentrations by applying simple probabilistic rules of particle interaction and combination. The forward reaction A + B? C is coded by calculating the probability that any A and B particles will occupy the same volume over some time interval. This becomes a convolution of the location densities of the two particles.

  3. Simulation of chemical reaction via particle tracking: Diffusion-limited versus thermodynamic rate-limited regimes

    Microsoft Academic Search

    David A. Benson; Mark M. Meerschaert

    2008-01-01

    Chemical reactions may be simulated without regard to local concentrations by applying simple probabilistic rules of particle interaction and combination. The forward reaction A + B-> C is coded by calculating the probability that any A and B particles will occupy the same volume over some time interval. This becomes a convolution of the location densities of the two particles.

  4. Direct Monte Carlo simulation of chemical reaction systems: Dissociation and recombination

    E-print Network

    Anderson, James B.

    Direct Monte Carlo simulation of chemical reaction systems: Dissociation and recombination Shannon of Physics. I. INTRODUCTION In earlier studies1­5 we have found the direct Monte Carlo simulation method6 Monte Carlo simulation of dissociation-recombination reac- tions of the type M AB M A B. These reactions

  5. Experimental simulation of chemical reactions between ZDDP tribofilms and steel surfaces during friction processes

    Microsoft Academic Search

    C. Minfray; T. Le Mogne; A. A. Lubrecht; J.-M. Martin

    2006-01-01

    Friction tests are performed in a controlled environment (Ultra High Vacuum), between steel surfaces and a ZDDP tribofilm\\u000a at different contact severities. According to AES analyses, evidence of chemical reactions activated by friction is given.\\u000a The reaction of the ZDDP tribofilm with the native iron oxide could partially explain its antiwear behavior.

  6. 15 CFR 713.3 - Annual declaration and reporting requirements for exports and imports of Schedule 2 chemicals.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...and imports of Schedule 2 chemicals. 713.3 Section 713...Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS...ACTIVITIES INVOLVING SCHEDULE 2 CHEMICALS § 713.3 Annual...

  7. 15 CFR 713.3 - Annual declaration and reporting requirements for exports and imports of Schedule 2 chemicals.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...and imports of Schedule 2 chemicals. 713.3 Section 713...Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS...ACTIVITIES INVOLVING SCHEDULE 2 CHEMICALS § 713.3 Annual...

  8. 15 CFR 713.3 - Annual declaration and reporting requirements for exports and imports of Schedule 2 chemicals.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...and imports of Schedule 2 chemicals. 713.3 Section 713...Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS...ACTIVITIES INVOLVING SCHEDULE 2 CHEMICALS § 713.3 Annual...

  9. 15 CFR 713.3 - Annual declaration and reporting requirements for exports and imports of Schedule 2 chemicals.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...and imports of Schedule 2 chemicals. 713.3 Section 713...Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS...ACTIVITIES INVOLVING SCHEDULE 2 CHEMICALS § 713.3 Annual...

  10. 15 CFR 713.3 - Annual declaration and reporting requirements for exports and imports of Schedule 2 chemicals.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...for exports and imports of Schedule 2 chemicals. 713.3 Section 713.3 Commerce...SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ACTIVITIES INVOLVING SCHEDULE 2 CHEMICALS § 713.3 Annual...

  11. Polarization of molecular angular momentum in the chemical reactions Li + HF and F + HD

    NASA Astrophysics Data System (ADS)

    Krasilnikov, Mikhail B.; Popov, Ruslan S.; Roncero, Octavio; De Fazio, Dario; Cavalli, Simonetta; Aquilanti, Vincenzo; Vasyutinskii, Oleg S.

    2013-06-01

    The quantum mechanical approach to vector correlation of angular momentum orientation and alignment in chemical reactions [G. Balint-Kurti and O. S. Vasyutinskii, J. Phys. Chem. A 113, 14281 (2009)], 10.1021/jp902796v is applied to the molecular reagents and products of the Li + HF [L. Gonzalez-Sanchez, O. S. Vasyutinskii, A. Zanchet, C. Sanz-Sanz, and O. Roncero, Phys. Chem. Chem. Phys. 13, 13656 (2011)], 10.1039/c0cp02452j and F + HD [D. De Fazio, J. Lucas, V. Aquilanti, and S. Cavalli, Phys. Chem. Chem. Phys. 13, 8571 (2011)], 10.1039/c0cp02738c reactions for which accurate scattering information has become recently available through time-dependent and time-independent approaches. Application of the theory to two important particular cases of the reactive collisions has been considered: (i) the influence of the angular momentum polarization of reactants in the entrance channel on the spatial distribution of the products in the exit channel and (ii) angular momentum polarization of the products of the reaction between unpolarized reactants. In the former case, the role of the angular momentum alignment of the reactants is shown to be large, particularly when the angular momentum is perpendicular to the reaction scattering plane. In the latter case, the orientation and alignment of the product angular momentum was found to be significant and strongly dependent on the scattering angle. The calculation also reveals significant differences between the vector correlation properties of the two reactions under study which are due to difference in the reaction mechanisms. In the case of F + HD reaction, the branching ratio between HF and DF production points out interest in the insight gained into the detailed dynamics, when information is available either from exact quantum mechanical calculations or from especially designed experiments. Also, the geometrical arrangement for the experimental determination of the product angular momentum orientation and alignment based on a compact and convenient spherical tensor expression for the intensity of the resonance enhanced multiphoton ionization (REMPI 2 + 1) signal is suggested.

  12. Selection of substrata by juvenile Choromytilus chorus (Mytilidae): are chemical cues important?

    Microsoft Academic Search

    Andrew R. Davis; Carlos A. Moreno

    1995-01-01

    The importance of filamentous algae, and filamentous structures in general, to patterns of recruitment in mytilids is well documented. Surprisingly, the relative importance of physical and chemical cues in mediating this interaction has rarely been examined for mytilid larvae or plantigrades. Here we examine the distribution and abundance of three mytilid species on three common species of algae on the

  13. Reaction operators for spin-selective chemical reactions of radical pairs

    E-print Network

    Jonathan A. Jones; Kiminori Maeda; Peter J. Hore

    2011-03-30

    Spin-selective reactions of radical pairs have traditionally been modelled theoretically by adding phenomenological rate equations to the quantum mechanical equation of motion of the radical pair spin density matrix. More recently an alternative set of rate expressions, based on a quantum measurement approach, has been suggested. Here we show how these two reaction operators can be seen as limiting cases of a more general reaction scheme.

  14. Reaction operators for spin-selective chemical reactions of radical pairs

    E-print Network

    Jones, Jonathan A; Hore, Peter J

    2011-01-01

    Spin-selective reactions of radical pairs have traditionally been modelled theoretically by adding phenomenological rate equations to the quantum mechanical equation of motion of the radical pair spin density matrix. More recently an alternative set of rate expressions, based on a quantum measurement approach, has been suggested. Here we show how these two reaction operators can be seen as limiting cases of a more general reaction scheme.

  15. ABIOTIC REDUCTION REACTIONS OF ANTHROPOGENIC ORGANIC CHEMICALS IN ANAEROBIC SYSTEMS: A CRITICAL REVIEW

    EPA Science Inventory

    The review is predicated upon the need for a detailed process-level understanding of factors influencing the reduction of anthropogenic organic chemicals in natural waters. In particular, abiotic reductions of anthropogenic organic chemicals are reviewed. The most important reduc...

  16. Survey and assessment of heat of reaction type chemical heat pumps

    Microsoft Academic Search

    R. D. Sanders Jr.; D. F. Suciu; W. J. Toth; P. M. Wikoff

    1984-01-01

    The development of technology to augment a significant portion of the manufacturing fuel requirements with the low grade energy contained in the industrial process waste heat streams is discussed. The development of mechanical and chemical heat pumps for industrial application were investigated. The state-of-the-art and heat of reaction chemical heat pump systems (HRCHP) were assessed. Significant potential for such a

  17. Tunnelling chemical reactions of hydrogen isotopes in quantum solids

    NASA Astrophysics Data System (ADS)

    Khmelenko, V. V.; Bernard, E. P.; Vasiliev, S. À.; Lee, D. M.

    2007-12-01

    The kinetics of tunnelling reactions of hydrogen isotopes in solid molecular nanoclusters immersed in superfluid helium and the changes in the environment of the atoms during the course of these reactions are reviewed. Results of pulsed electron spin resonance show that a very large fraction (50%-60%) of the stabilised atoms reside on the surfaces of the nanoclusters. The results of studies of the recombination and the exotic behaviour of hydrogen atoms in a solid molecular hydrogen matrix at ultralow temperatures (0.15-0.9 K) are also discussed.

  18. High temperature chemical kinetic study of the H2-CO-CO2-NO reaction system

    NASA Technical Reports Server (NTRS)

    Jachimowski, C. J.

    1975-01-01

    An experimental study of the kinetics of the H2-CO-CO2-NO reaction system was made behind incident shock waves at temperatures of 2460 and 2950 K. The overall rate of the reaction was measured by monitoring radiation from the CO + O yields CO2 + h upoilon reaction. Correlation of these data with a detailed reaction mechanism showed that the high-temperature rate of the reaction N + OH yields NO + H can be described by the low-temperature (320 K) rate coefficient. Catalytic dissociation of molecular hydrogen was an important reaction under the tests conditions.

  19. Rate constants for chemical reactions in high-temperature nonequilibrium air

    NASA Technical Reports Server (NTRS)

    Jaffe, R. L.

    1986-01-01

    In the nonequilibrium atmospheric chemistry regime that will be encountered by the proposed Aeroassisted Orbital Transfer Vehicle in the upper atmosphere, where air density is too low for thermal and chemical equilibrium to be maintained, the detailed high temperature air chemistry plays a critical role in defining radiative and convective heating loads. Although vibrational and electronic temperatures remain low (less than 15,000 K), rotational and translational temperatures may reach 50,000 K. Attention is presently given to the effects of multiple temperatures on the magnitudes of various chemical reaction rate constants, for the cases of both bimolecular exchange reactions and collisional excitation and dissociation reactions.

  20. Kinetics of Heterogeneous Chemical Reactions: A Theoretical Model for the Accumulation of Pesticides in Soil

    PubMed Central

    Lin, S. H.; Sahai, R.; Eyring, H.

    1971-01-01

    A theoretical model for the accumulation of pesticides in soil has been proposed and discussed from the viewpoint of heterogeneous reaction kinetics with a basic aim to understand the complex nature of soil processes relating to the environmental pollution. In the bulk of soil, the pesticide disappears by diffusion and a chemical reaction; the rate processes considered on the surface of soil are diffusion, chemical reaction, vaporization, and regular pesticide application. The differential equations involved have been solved analytically by the Laplace-transform method. PMID:5279519